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Datta R. Enzymatic degradation of cellulose in soil: A review. Heliyon 2024; 10:e24022. [PMID: 38234915 PMCID: PMC10792583 DOI: 10.1016/j.heliyon.2024.e24022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/13/2023] [Accepted: 01/02/2024] [Indexed: 01/19/2024] Open
Abstract
Cellulose degradation is a critical process in soil ecosystems, playing a vital role in nutrient cycling and organic matter decomposition. Enzymatic degradation of cellulosic biomass is the most sustainable and green method of producing liquid biofuel. It has gained intensive research interest with future perspective as the majority of terrestrial lignocellulose biomass has a great potential to be used as a source of bioenergy. However, the recalcitrant nature of lignocellulose limits its use as a source of energy. Noteworthy enough, enzymatic conversion of cellulose biomass could be a leading future technology. Fungal enzymes play a central role in cellulose degradation. Our understanding of fungal cellulases has substantially redirected in the past few years with the discovery of a new class of enzymes and Cellulosome. Efforts have been made from time to time to develop an economically viable method of cellulose degradation. This review provides insights into the current state of knowledge regarding cellulose degradation in soil and identifies areas where further research is needed.
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Affiliation(s)
- Rahul Datta
- Department of Geology and Pedology, Faculty of Forestry and Wood Technology. Mendel University In Brno, Czech Republic
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2
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Dementiev A, Lillington SP, Jin S, Kim Y, Jedrzejczak R, Michalska K, Joachimiak A, O'Malley MA. Structure and enzymatic characterization of CelD endoglucanase from the anaerobic fungus Piromyces finnis. Appl Microbiol Biotechnol 2023; 107:5999-6011. [PMID: 37548665 PMCID: PMC10485095 DOI: 10.1007/s00253-023-12684-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 06/24/2023] [Accepted: 06/29/2023] [Indexed: 08/08/2023]
Abstract
Anaerobic fungi found in the guts of large herbivores are prolific biomass degraders whose genomes harbor a wealth of carbohydrate-active enzymes (CAZymes), of which only a handful are structurally or biochemically characterized. Here, we report the structure and kinetic rate parameters for a glycoside hydrolase (GH) family 5 subfamily 4 enzyme (CelD) from Piromyces finnis, a modular, cellulosome-incorporated endoglucanase that possesses three GH5 domains followed by two C-terminal fungal dockerin domains (double dockerin). We present the crystal structures of an apo wild-type CelD GH5 catalytic domain and its inactive E154A mutant in complex with cellotriose at 2.5 and 1.8 Å resolution, respectively, finding the CelD GH5 catalytic domain adopts the (β/α)8-barrel fold common to many GH5 enzymes. Structural superimposition of the apo wild-type structure with the E154A mutant-cellotriose complex supports a catalytic mechanism in which the E154 carboxylate side chain acts as an acid/base and E278 acts as a complementary nucleophile. Further analysis of the cellotriose binding pocket highlights a binding groove lined with conserved aromatic amino acids that when docked with larger cellulose oligomers is capable of binding seven glucose units and accommodating branched glucan substrates. Activity analyses confirm P. finnis CelD can hydrolyze mixed linkage glucan and xyloglucan, as well as carboxymethylcellulose (CMC). Measured kinetic parameters show the P. finnis CelD GH5 catalytic domain has CMC endoglucanase activity comparable to other fungal endoglucanases with kcat = 6.0 ± 0.6 s-1 and Km = 7.6 ± 2.1 g/L CMC. Enzyme kinetics were unperturbed by the addition or removal of the native C-terminal dockerin domains as well as the addition of a non-native N-terminal dockerin, suggesting strict modularity among the domains of CelD. KEY POINTS: • Anaerobic fungi host a wealth of industrially useful enzymes but are understudied. • P. finnis CelD has endoglucanase activity and structure common to GH5_4 enzymes. • CelD's kinetics do not change with domain fusion, exhibiting high modularity.
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Affiliation(s)
- Alexey Dementiev
- Structural Biology Center, X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Stephen P Lillington
- Department of Chemical Engineering, University of California, Santa Barbara, CA, USA
| | - Shiyan Jin
- Department of Chemical Engineering, University of California, Santa Barbara, CA, USA
| | - Youngchang Kim
- Structural Biology Center, X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Robert Jedrzejczak
- Structural Biology Center, X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Karolina Michalska
- Structural Biology Center, X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Andrzej Joachimiak
- Structural Biology Center, X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Michelle A O'Malley
- Department of Chemical Engineering, University of California, Santa Barbara, CA, USA.
- Biological Engineering Program, University of California, Santa Barbara, CA, USA.
- Joint BioEnergy Institute (JBEI), Emeryville, CA, 94608, USA.
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3
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Anderson AC, Stangherlin S, Pimentel KN, Weadge JT, Clarke AJ. The SGNH hydrolase family: a template for carbohydrate diversity. Glycobiology 2022; 32:826-848. [PMID: 35871440 PMCID: PMC9487903 DOI: 10.1093/glycob/cwac045] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 06/20/2022] [Accepted: 07/05/2022] [Indexed: 11/14/2022] Open
Abstract
The substitution and de-substitution of carbohydrate materials are important steps in the biosynthesis and/or breakdown of a wide variety of biologically important polymers. The SGNH hydrolase superfamily is a group of related and well-studied proteins with a highly conserved catalytic fold and mechanism composed of 16 member families. SGNH hydrolases can be found in vertebrates, plants, fungi, bacteria, and archaea, and play a variety of important biological roles related to biomass conversion, pathogenesis, and cell signaling. The SGNH hydrolase superfamily is chiefly composed of a diverse range of carbohydrate-modifying enzymes, including but not limited to the carbohydrate esterase families 2, 3, 6, 12 and 17 under the carbohydrate-active enzyme classification system and database (CAZy.org). In this review, we summarize the structural and functional features that delineate these subfamilies of SGNH hydrolases, and which generate the wide variety of substrate preferences and enzymatic activities observed of these proteins to date.
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Affiliation(s)
- Alexander C Anderson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
| | - Stefen Stangherlin
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo N2L3C5, Canada
| | - Kyle N Pimentel
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
| | - Joel T Weadge
- Department of Biology, Wilfrid Laurier University, Waterloo N2L3C5, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo N2L3C5, Canada
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Abstract
Cellulosomes are elaborate multienzyme complexes capable of efficiently deconstructing lignocellulosic substrates, produced by cellulolytic anaerobic microorganisms, colonizing a large variety of ecological niches. These macromolecular structures have a modular architecture and are composed of two main elements: the cohesin-bearing scaffoldins, which are non-catalytic structural proteins, and the various dockerin-bearing enzymes that tenaciously bind to the scaffoldins. Cellulosome assembly is mediated by strong and highly specific interactions between the cohesin modules, present in the scaffoldins, and the dockerin modules, present in the catalytic units. Cellulosomal architecture and composition varies between species and can even change within the same organism. These differences seem to be largely influenced by external factors, including the nature of the available carbon-source. Even though cellulosome producing organisms are relatively few, the development of new genomic and proteomic technologies has allowed the identification of cellulosomal components in many archea, bacteria and even some primitive eukaryotes. This reflects the importance of this cellulolytic strategy and suggests that cohesin-dockerin interactions could be involved in other non-cellulolytic processes. Due to their building-block nature and highly cellulolytic capabilities, cellulosomes hold many potential biotechnological applications, such as the conversion of lignocellulosic biomass in the production of biofuels or the development of affinity based technologies.
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Affiliation(s)
- Victor D Alves
- CIISA, Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal
| | - Carlos M G A Fontes
- CIISA, Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal
| | - Pedro Bule
- CIISA, Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal.
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Hess M, Paul SS, Puniya AK, van der Giezen M, Shaw C, Edwards JE, Fliegerová K. Anaerobic Fungi: Past, Present, and Future. Front Microbiol 2020; 11:584893. [PMID: 33193229 PMCID: PMC7609409 DOI: 10.3389/fmicb.2020.584893] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 09/29/2020] [Indexed: 11/13/2022] Open
Abstract
Anaerobic fungi (AF) play an essential role in feed conversion due to their potent fiber degrading enzymes and invasive growth. Much has been learned about this unusual fungal phylum since the paradigm shifting work of Colin Orpin in the 1970s, when he characterized the first AF. Molecular approaches targeting specific phylogenetic marker genes have facilitated taxonomic classification of AF, which had been previously been complicated by the complex life cycles and associated morphologies. Although we now have a much better understanding of their diversity, it is believed that there are still numerous genera of AF that remain to be described in gut ecosystems. Recent marker-gene based studies have shown that fungal diversity in the herbivore gut is much like the bacterial population, driven by host phylogeny, host genetics and diet. Since AF are major contributors to the degradation of plant material ingested by the host animal, it is understandable that there has been great interest in exploring the enzymatic repertoire of these microorganisms in order to establish a better understanding of how AF, and their enzymes, can be used to improve host health and performance, while simultaneously reducing the ecological footprint of the livestock industry. A detailed understanding of AF and their interaction with other gut microbes as well as the host animal is essential, especially when production of affordable high-quality protein and other animal-based products needs to meet the demands of an increasing human population. Such a mechanistic understanding, leading to more sustainable livestock practices, will be possible with recently developed -omics technologies that have already provided first insights into the different contributions of the fungal and bacterial population in the rumen during plant cell wall hydrolysis.
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Affiliation(s)
- Matthias Hess
- Systems Microbiology & Natural Product Discovery Laboratory, Department of Animal Science, University of California, Davis, Davis, CA, United States
| | - Shyam S. Paul
- Gut Microbiome Lab, ICAR-Directorate of Poultry Research, Indian Council of Agricultural Research, Hyderabad, India
| | - Anil K. Puniya
- Anaerobic Microbiology Lab, ICAR-National Dairy Research Institute, Dairy Microbiology Division, ICAR-National Dairy Research Institute, Karnal, India
| | - Mark van der Giezen
- Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, Stavanger, Norway
| | - Claire Shaw
- Systems Microbiology & Natural Product Discovery Laboratory, Department of Animal Science, University of California, Davis, Davis, CA, United States
| | - Joan E. Edwards
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands
| | - Kateřina Fliegerová
- Laboratory of Anaerobic Microbiology, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Prague, Czechia
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6
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Chang J, Park H. Nucleotide and protein researches on anaerobic fungi during four decades. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2020; 62:121-140. [PMID: 32292921 PMCID: PMC7142291 DOI: 10.5187/jast.2020.62.2.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/07/2020] [Accepted: 03/07/2020] [Indexed: 01/26/2023]
Abstract
Anaerobic fungi habitat in the gastrointestinal tract of foregut fermenters or
hindgut fermenters and degrade fibrous plant biomass through the hydrolysis
reactions with a wide variety of cellulolytic enzymes and physical penetration
through fiber matrix with their rhizoids. To date, seventeen genera have been
described in family Neocallimasticaceae, class
Neocallimastigomycetes, phylum
Neocallimastigomycota and one genus has been described in
phylum Neocallimastigomycota. In National Center for
Biotechnology Information (NCBI) database (DB), 23,830 nucleotide sequences and
59,512 protein sequences have been deposited and most of them were originated
from Piromyces, Neocallimastix and
Anaeromyces. Most of protein sequences (44,025) were
acquired with PacBio next generation sequencing system. The whole genome
sequences of Anaeromyces robustus, Neocallimastix
californiae, Pecoramyces ruminantium,
Piromyces finnis and Piromyces sp. E2 are
available in Joint Genome Institute (JGI) database. According to the results of
protein prediction, average Isoelectric points (pIs) were ranged from 5.88
(Anaeromyces) to 6.57 (Piromyces) and
average molecular weights were ranged from 38.7 kDa
(Orpinomyces) to 56.6 kDa (Piromyces). In
Carbohydrate-Active enZYmes (CAZY) database, glycoside hydrolases (36),
carbohydrate binding module (11), carbohydrate esterases (8),
glycosyltransferase (5) and polysaccharide lyases (3) from anaerobic fungi were
registered. During four decades, 1,031 research articles about anaerobic fungi
were published and 444 and 719 articles were available in PubMed (PM) and PubMed
Central (PMC) DB.
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Affiliation(s)
- Jongsoo Chang
- Department of Agricultural Sciences, Korea National Open University, Seoul 03087, Korea
| | - Hyunjin Park
- Department of Agricultural Sciences, Korea National Open University, Seoul 03087, Korea
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7
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Leveraging anaerobic fungi for biotechnology. Curr Opin Biotechnol 2019; 59:103-110. [DOI: 10.1016/j.copbio.2019.03.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/19/2019] [Accepted: 03/12/2019] [Indexed: 12/30/2022]
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8
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Moraïs S, Mizrahi I. Islands in the stream: from individual to communal fiber degradation in the rumen ecosystem. FEMS Microbiol Rev 2019; 43:362-379. [PMID: 31050730 PMCID: PMC6606855 DOI: 10.1093/femsre/fuz007] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 04/05/2019] [Indexed: 12/20/2022] Open
Abstract
The herbivore rumen ecosystem constitutes an extremely efficient degradation machinery for the intricate chemical structure of fiber biomass, thus, enabling the hosting animal to digest its feed. The challenging task of deconstructing and metabolizing fiber is performed by microorganisms inhabiting the rumen. Since most of the ingested feed is comprised of plant fiber, these fiber-degrading microorganisms are of cardinal importance to the ecology of the rumen microbial community and to the hosting animal, and have a great impact on our environment and food sustainability. We summarize herein the enzymological fundamentals of fiber degradation, how the genes encoding these enzymes are spread across fiber-degrading microbes, and these microbes' interactions with other members of the rumen microbial community and potential effect on community structure. An understanding of these concepts has applied value for agriculture and our environment, and will also contribute to a better understanding of microbial ecology and evolution in anaerobic ecosystems.
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Affiliation(s)
- Sarah Moraïs
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Sderot Ben Gurion 1, Beer-Sheva 8499000, Israel
| | - Itzhak Mizrahi
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Sderot Ben Gurion 1, Beer-Sheva 8499000, Israel
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9
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Lange L, Barrett K, Pilgaard B, Gleason F, Tsang A. Enzymes of early-diverging, zoosporic fungi. Appl Microbiol Biotechnol 2019; 103:6885-6902. [PMID: 31309267 PMCID: PMC6690862 DOI: 10.1007/s00253-019-09983-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 06/12/2019] [Accepted: 06/13/2019] [Indexed: 11/26/2022]
Abstract
The secretome, the complement of extracellular proteins, is a reflection of the interaction of an organism with its host or substrate, thus a determining factor for the organism’s fitness and competitiveness. Hence, the secretome impacts speciation and organismal evolution. The zoosporic Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, and Cryptomycota represent the earliest diverging lineages of the Fungal Kingdom. The review describes the enzyme compositions of these zoosporic fungi, underscoring the enzymes involved in biomass degradation. The review connects the lifestyle and substrate affinities of the zoosporic fungi to the secretome composition by examining both classical phenotypic investigations and molecular/genomic-based studies. The carbohydrate-active enzyme profiles of 19 genome-sequenced species are summarized. Emphasis is given to recent advances in understanding the functional role of rumen fungi, the basis for the devastating chytridiomycosis, and the structure of fungal cellulosome. The approach taken by the review enables comparison of the secretome enzyme composition of anaerobic versus aerobic early-diverging fungi and comparison of enzyme portfolio of specialized parasites, pathogens, and saprotrophs. Early-diverging fungi digest most major types of biopolymers: cellulose, hemicellulose, pectin, chitin, and keratin. It is thus to be expected that early-diverging fungi in its entirety represents a rich and diverse pool of secreted, metabolic enzymes. The review presents the methods used for enzyme discovery, the diversity of enzymes found, the status and outlook for recombinant production, and the potential for applications. Comparative studies on the composition of secretome enzymes of early-diverging fungi would contribute to unraveling the basal lineages of fungi.
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Affiliation(s)
- Lene Lange
- Bioeconomy, Research & Advisory, Karensgade 5, Valby, DK-2500, Copenhagen, Denmark.
| | - Kristian Barrett
- Protein Chemistry and Enzyme Technology, Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads 221, DK-2800, Kgs. Lyngby, Denmark
| | - Bo Pilgaard
- Protein Chemistry and Enzyme Technology, Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads 221, DK-2800, Kgs. Lyngby, Denmark
| | - Frank Gleason
- School of Life and Environmental Sciences, University of Sydney, Sydney, 2006, Australia
| | - Adrian Tsang
- Centre for Structural and Functional Genomics, Concordia University, Montreal, QC, H4B1R6, Canada
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10
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Badhan A, Huang J, Wang Y, Abbott DW, Di Falco M, Tsang A, McAllister T. Saccharification efficiencies of multi-enzyme complexes produced by aerobic fungi. N Biotechnol 2018; 46:1-6. [PMID: 29803771 DOI: 10.1016/j.nbt.2018.05.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 05/08/2018] [Accepted: 05/09/2018] [Indexed: 11/16/2022]
Abstract
In the present study, we have characterized high molecular weight multi-enzyme complexes in two commercial enzymes produced by Trichoderma reesei (Spezyme CP) and Penicillium funiculosum (Accellerase XC). We successfully identified 146-1000 kDa complexes using Blue native polyacrylamide gel electrophoresis (BN-PAGE) to fractionate the protein profile in both preparations. Identified complexes dissociated into lower molecular weight constituents when loaded on SDS PAGE. Unfolding of the secondary structure of multi-enzyme complexes with trimethylamine (pH >10) suggested that they were not a result of unspecific protein aggregation. Cellulase (CMCase) profiles of extracts of BN-PAGE fractionated protein bands confirmed cellulase activity within the multi-enzyme complexes. A microassay was used to identify protein bands that promoted high levels of glucose release from barley straw. Those with high saccharification yield were subjected to LC-MS analysis to identify the principal enzymatic activities responsible. The results suggest that secretion of proteins by aerobic fungi leads to the formation of high molecular weight multi-enzyme complexes that display activity against carboxymethyl cellulose and barley straw.
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Affiliation(s)
- Ajay Badhan
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Jiangli Huang
- Institute of Biological Resources, Jiangxi Academy of Sciences, Nanchang, 330096, China
| | - Yuxi Wang
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - D Wade Abbott
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Marcos Di Falco
- Centre for Structural and Functional Genomics, Concordia University, Montreal, Quebec, H4B 1R6, Canada
| | - Adrian Tsang
- Institute of Biological Resources, Jiangxi Academy of Sciences, Nanchang, 330096, China
| | - Tim McAllister
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada.
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11
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Gruninger RJ, Nguyen TTM, Reid ID, Yanke JL, Wang P, Abbott DW, Tsang A, McAllister T. Application of Transcriptomics to Compare the Carbohydrate Active Enzymes That Are Expressed by Diverse Genera of Anaerobic Fungi to Degrade Plant Cell Wall Carbohydrates. Front Microbiol 2018; 9:1581. [PMID: 30061875 PMCID: PMC6054980 DOI: 10.3389/fmicb.2018.01581] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 06/25/2018] [Indexed: 01/05/2023] Open
Abstract
The efficiency with which the anaerobic fungi (phylum Neocallimastigomycota) degrade plant biomass is well-recognized and in recent years has received renewed interest. To further understand the biological mechanisms that are utilized by the rumen anaerobic fungi to break down lignocellulose, we have used a transcriptomic approach to examine carbohydrate digestion by Neocallimastix frontalis, Piromyces rhizinflata, Orpinomyces joyonii, and Anaeromyces mucronatus cultured on several carbon sources. The number of predicted unique transcripts ranged from 6,633 to 12,751. Pfam domains were identified in 62–70% of the fungal proteins and were linked to gene ontology terms to infer the biological function of the transcripts. Most of the predicted functions are consistent across species suggesting a similar overall strategy evolved for successful colonization of the rumen. However, the presence of differential profiles in enzyme classes suggests that there may be also be niche specialization. All fungal species were found to express an extensive array of transcripts encoding carbohydrate active enzymes (CAZymes) ranging from 8.3 to 11.3% of the transcriptome. CAZyme families involved in hemicellulose digestion were the most abundant across all four fungi. This study provides additional insight into how anaerobic fungi have evolved to become specialists at breaking down the plant cell wall in the complex and, strictly anaerobic rumen ecosystem.
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Affiliation(s)
- Robert J Gruninger
- Lethbridge Research and Development Centre, Agriculture and Agri-Foods Canada, Lethbridge, AB, Canada
| | - Thi T M Nguyen
- Centre for Structural and Functional Genomics, Concordia University, Montreal, QC, Canada
| | - Ian D Reid
- Centre for Structural and Functional Genomics, Concordia University, Montreal, QC, Canada
| | - Jay L Yanke
- Lethbridge Research and Development Centre, Agriculture and Agri-Foods Canada, Lethbridge, AB, Canada
| | - Pan Wang
- Lethbridge Research and Development Centre, Agriculture and Agri-Foods Canada, Lethbridge, AB, Canada
| | - Denis W Abbott
- Lethbridge Research and Development Centre, Agriculture and Agri-Foods Canada, Lethbridge, AB, Canada
| | - Adrian Tsang
- Centre for Structural and Functional Genomics, Concordia University, Montreal, QC, Canada
| | - Tim McAllister
- Lethbridge Research and Development Centre, Agriculture and Agri-Foods Canada, Lethbridge, AB, Canada
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12
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Seppälä S, Wilken SE, Knop D, Solomon KV, O’Malley MA. The importance of sourcing enzymes from non-conventional fungi for metabolic engineering and biomass breakdown. Metab Eng 2017; 44:45-59. [DOI: 10.1016/j.ymben.2017.09.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/16/2017] [Accepted: 09/16/2017] [Indexed: 10/18/2022]
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13
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Haitjema CH, Gilmore SP, Henske JK, Solomon KV, de Groot R, Kuo A, Mondo SJ, Salamov AA, LaButti K, Zhao Z, Chiniquy J, Barry K, Brewer HM, Purvine SO, Wright AT, Hainaut M, Boxma B, van Alen T, Hackstein JHP, Henrissat B, Baker SE, Grigoriev IV, O'Malley MA. A parts list for fungal cellulosomes revealed by comparative genomics. Nat Microbiol 2017; 2:17087. [PMID: 28555641 DOI: 10.1038/nmicrobiol.2017.87] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 04/25/2017] [Indexed: 12/16/2022]
Abstract
Cellulosomes are large, multiprotein complexes that tether plant biomass-degrading enzymes together for improved hydrolysis1. These complexes were first described in anaerobic bacteria, where species-specific dockerin domains mediate the assembly of enzymes onto cohesin motifs interspersed within protein scaffolds1. The versatile protein assembly mechanism conferred by the bacterial cohesin-dockerin interaction is now a standard design principle for synthetic biology2,3. For decades, analogous structures have been reported in anaerobic fungi, which are known to assemble by sequence-divergent non-catalytic dockerin domains (NCDDs)4. However, the components, modular assembly mechanism and functional role of fungal cellulosomes remain unknown5,6. Here, we describe a comprehensive set of proteins critical to fungal cellulosome assembly, including conserved scaffolding proteins unique to the Neocallimastigomycota. High-quality genomes of the anaerobic fungi Anaeromyces robustus, Neocallimastix californiae and Piromyces finnis were assembled with long-read, single-molecule technology. Genomic analysis coupled with proteomic validation revealed an average of 312 NCDD-containing proteins per fungal strain, which were overwhelmingly carbohydrate active enzymes (CAZymes), with 95 large fungal scaffoldins identified across four genera that bind to NCDDs. Fungal dockerin and scaffoldin domains have no similarity to their bacterial counterparts, yet several catalytic domains originated via horizontal gene transfer with gut bacteria. However, the biocatalytic activity of anaerobic fungal cellulosomes is expanded by the inclusion of GH3, GH6 and GH45 enzymes. These findings suggest that the fungal cellulosome is an evolutionarily chimaeric structure-an independently evolved fungal complex that co-opted useful activities from bacterial neighbours within the gut microbiome.
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Affiliation(s)
- Charles H Haitjema
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - Sean P Gilmore
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - John K Henske
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - Kevin V Solomon
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - Randall de Groot
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - Alan Kuo
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Stephen J Mondo
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Asaf A Salamov
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Kurt LaButti
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Zhiying Zhao
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Jennifer Chiniquy
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Kerrie Barry
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA
| | - Heather M Brewer
- Environmental Molecular Sciences Laboratory, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Samuel O Purvine
- Environmental Molecular Sciences Laboratory, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Aaron T Wright
- Biological Sciences Division, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Matthieu Hainaut
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, 13288 Marseille, France.,INRA, USC 1408 AFMB, Marseille, France
| | - Brigitte Boxma
- Department of Evolutionary Microbiology, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Theo van Alen
- Department of Evolutionary Microbiology, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Johannes H P Hackstein
- Department of Evolutionary Microbiology, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, 13288 Marseille, France.,INRA, USC 1408 AFMB, Marseille, France.,Department of Biological Sciences, King Abdulaziz University, 23218 Jeddah, Saudi Arabia
| | - Scott E Baker
- Environmental Molecular Sciences Laboratory, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Igor V Grigoriev
- US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA.,Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
| | - Michelle A O'Malley
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
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14
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Ladevèze S, Laville E, Despres J, Mosoni P, Potocki-Véronèse G. Mannoside recognition and degradation by bacteria. Biol Rev Camb Philos Soc 2016; 92:1969-1990. [PMID: 27995767 DOI: 10.1111/brv.12316] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 11/01/2016] [Accepted: 11/11/2016] [Indexed: 11/29/2022]
Abstract
Mannosides constitute a vast group of glycans widely distributed in nature. Produced by almost all organisms, these carbohydrates are involved in numerous cellular processes, such as cell structuration, protein maturation and signalling, mediation of protein-protein interactions and cell recognition. The ubiquitous presence of mannosides in the environment means they are a reliable source of carbon and energy for bacteria, which have developed complex strategies to harvest them. This review focuses on the various mannosides that can be found in nature and details their structure. It underlines their involvement in cellular interactions and finally describes the latest discoveries regarding the catalytic machinery and metabolic pathways that bacteria have developed to metabolize them.
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Affiliation(s)
- Simon Ladevèze
- LISBP, Université de Toulouse, CNRS, INRA, INSA, 31077, Toulouse, France
| | - Elisabeth Laville
- LISBP, Université de Toulouse, CNRS, INRA, INSA, 31077, Toulouse, France
| | - Jordane Despres
- INRA, UR454 Microbiologie, F-63122, Saint-Genès Champanelle, France
| | - Pascale Mosoni
- INRA, UR454 Microbiologie, F-63122, Saint-Genès Champanelle, France
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15
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Abstract
Extraction of sugar is the rate-limiting step in converting unpretreated biomass into value-added products through microbial fermentation. Both anaerobic fungi and anaerobic bacteria have evolved to produce large multi-cellulase complexes referred to as cellulosomes, which are powerful machines for biomass deconstruction. Characterization of bacterial cellulosomes has inspired synthetic "designer" cellulosomes, consisting of parts discovered from the native system that have proven useful for cellulose depolymerization. By contrast, the multi-cellulase complexes produced by anaerobic fungi are much more poorly understood, and to date their composition, architecture, and enzyme tethering mechanism remain unknown and heavily debated. Here, we compare current knowledge pertaining to the cellulosomes produced by both bacteria and fungi, including their application to synthetic enzyme-tethered systems for tunneled biocatalysis. We highlight gaps in knowledge and opportunities for discovery, especially pertaining to the potential of fungal cellulosome-inspired systems.
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Affiliation(s)
- Sean P Gilmore
- a Department of Chemical Engineering ; University of California ; Santa Barbara , CA USA
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16
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Lakhundi S, Siddiqui R, Khan NA. Cellulose degradation: a therapeutic strategy in the improved treatment of Acanthamoeba infections. Parasit Vectors 2015; 8:23. [PMID: 25586209 PMCID: PMC4300153 DOI: 10.1186/s13071-015-0642-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 01/05/2015] [Indexed: 11/10/2022] Open
Abstract
Acanthamoeba is an opportunistic free-living amoeba that can cause blinding keratitis and fatal brain infection. Early diagnosis, followed by aggressive treatment is a pre-requisite in the successful treatment but even then the prognosis remains poor. A major drawback during the course of treatment is the ability of the amoeba to enclose itself within a shell (a process known as encystment), making it resistant to chemotherapeutic agents. As the cyst wall is partly made of cellulose, thus cellulose degradation offers a potential therapeutic strategy in the effective targeting of trophozoite encased within the cyst walls. Here, we present a comprehensive report on the structure of cellulose and cellulases, as well as known cellulose degradation mechanisms with an eye to target the Acanthamoeba cyst wall. The disruption of the cyst wall will make amoeba (concealed within) susceptible to chemotherapeutic agents, and at the very least inhibition of the excystment process will impede infection recurrence, as we bring these promising drug targets into focus so that they can be explored to their fullest.
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Affiliation(s)
- Sahreena Lakhundi
- Department of Biological and Biomedical Sciences, Aga Khan University, Stadium Road, Karachi, Pakistan.
| | - Ruqaiyyah Siddiqui
- Department of Biological and Biomedical Sciences, Aga Khan University, Stadium Road, Karachi, Pakistan.
| | - Naveed Ahmed Khan
- Department of Biological and Biomedical Sciences, Aga Khan University, Stadium Road, Karachi, Pakistan.
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17
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Ghosh A, Verma AK, Gautam S, Gupta MN, Goyal A. Structure and functional investigation of ligand binding by a family 35 carbohydrate binding module (CtCBM35) of β-mannanase of family 26 glycoside hydrolase from Clostridium thermocellum. BIOCHEMISTRY (MOSCOW) 2014; 79:672-86. [DOI: 10.1134/s0006297914070098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Purification and characterization of a cellulolytic multienzyme complex produced by Neocallimastix patriciarum J11. Biochem Biophys Res Commun 2014; 451:190-5. [PMID: 25073115 DOI: 10.1016/j.bbrc.2014.07.088] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 07/19/2014] [Indexed: 11/24/2022]
Abstract
Understanding the roles of the components of the multienzyme complex of the anaerobial cellulase system, acting on complex substrates, is crucial to the development of efficient cellulase systems for industrial applications such as converting lignocellulose to sugars for bioethanol production. In this study, we purified the multienzyme complex of Neocallimastix patriciarum J11 from a broth through cellulose affinity purification. The multienzyme complex is composed of at least 12 comprised proteins, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Eight of these constituents have demonstrated β-glucanase activity on zymogram analysis. The multienzyme complex contained scaffoldings that respond to the gathering of the cellulolytic components. The levels and subunit ratio of the multienzyme complex from N. patriciarum J11 might have been affected by their utilized carbon sources, whereas the components of the complexes were consistent. The trypsin-digested peptides of six proteins were matched to the sequences of cellulases originating from rumen fungi, based on identification through liquid chromatography/mass spectrometry, revealing that at least three types of cellulase, including one endoglucanase and two exoglucanases, could be found in the multienzyme complex of N. patriciarum J11. The cellulolytic subunits could hydrolyze synergistically on both the internal bonds and the reducing and nonreducing ends of cellulose. Based on our research, our findings are the first to depict the composition of the multienzyme complex produced by N. patriciarum J11, and this complex is composed of scaffoldin and three types of cellulase.
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19
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Wang HC, Chen YC, Huang CT, Hseu RS. Cloning and characterization of a thermostable and pH-stable cellobiohydrolase from Neocallimastix patriciarum J11. Protein Expr Purif 2013; 90:153-9. [PMID: 23770555 DOI: 10.1016/j.pep.2013.06.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/02/2013] [Accepted: 06/05/2013] [Indexed: 11/28/2022]
Abstract
An 1888-bp cDNA designated celA, isolated from a cDNA library of Neocallimastix patriciarum J11 was cloned. The celA had an open reading frame of 1530 bp encoding J11 CelA of 510 amino acids. The primary structure analysis of J11 CelA revealed a complete cellulose-binding domain at the N-terminal, followed by an Asn, Ala, Gly, Gln and Pro-rich linker and ending with a C-terminal glycosyl hydrolase family 6 catalytic domain. The mature J11 CelA was overexpressed in Escherichia coli and purified to homogeneity. This enzyme had high specific activities towards barley β-glucan and lichenan, low toward carboxymethyl cellulose (CMC), Avicel, and H3PO4-swollen Avicel (PSA). The product of Avicel hydrolysis was cellobiose indicating that J11 CelA is a typical cellobiohydrolase. The recombinant J11 CelA had an optimal pH of 6.0 and was stable over a wide range of pH (5.2-11.3). The enzyme showed an optimal temperature of 50°C and was still maintained approximately 50% of the maximum activity in response to the treatment at 70°C for 1h. Cobalt and Fe(3+) at 1 mM greatly activated the enzyme activity. As a thermostable and pH stable enzyme with crystalline cellulose-degrading activity, J11 CelA is a potential candidate for the bioethanol industry.
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Affiliation(s)
- Hui-Chang Wang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
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20
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The genome of the anaerobic fungus Orpinomyces sp. strain C1A reveals the unique evolutionary history of a remarkable plant biomass degrader. Appl Environ Microbiol 2013; 79:4620-34. [PMID: 23709508 DOI: 10.1128/aem.00821-13] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Anaerobic gut fungi represent a distinct early-branching fungal phylum (Neocallimastigomycota) and reside in the rumen, hindgut, and feces of ruminant and nonruminant herbivores. The genome of an anaerobic fungal isolate, Orpinomyces sp. strain C1A, was sequenced using a combination of Illumina and PacBio single-molecule real-time (SMRT) technologies. The large genome (100.95 Mb, 16,347 genes) displayed extremely low G+C content (17.0%), large noncoding intergenic regions (73.1%), proliferation of microsatellite repeats (4.9%), and multiple gene duplications. Comparative genomic analysis identified multiple genes and pathways that are absent in Dikarya genomes but present in early-branching fungal lineages and/or nonfungal Opisthokonta. These included genes for posttranslational fucosylation, the production of specific intramembrane proteases and extracellular protease inhibitors, the formation of a complete axoneme and intraflagellar trafficking machinery, and a near-complete focal adhesion machinery. Analysis of the lignocellulolytic machinery in the C1A genome revealed an extremely rich repertoire, with evidence of horizontal gene acquisition from multiple bacterial lineages. Experimental analysis indicated that strain C1A is a remarkable biomass degrader, capable of simultaneous saccharification and fermentation of the cellulosic and hemicellulosic fractions in multiple untreated grasses and crop residues examined, with the process significantly enhanced by mild pretreatments. This capability, acquired during its separate evolutionary trajectory in the rumen, along with its resilience and invasiveness compared to prokaryotic anaerobes, renders anaerobic fungi promising agents for consolidated bioprocessing schemes in biofuels production.
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21
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Couturier M, Roussel A, Rosengren A, Leone P, Stålbrand H, Berrin JG. Structural and biochemical analyses of glycoside hydrolase families 5 and 26 β-(1,4)-mannanases from Podospora anserina reveal differences upon manno-oligosaccharide catalysis. J Biol Chem 2013; 288:14624-14635. [PMID: 23558681 DOI: 10.1074/jbc.m113.459438] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The microbial deconstruction of the plant cell wall is a key biological process that is of increasing importance with the development of a sustainable biofuel industry. The glycoside hydrolase families GH5 (PaMan5A) and GH26 (PaMan26A) endo-β-1,4-mannanases from the coprophilic ascomycete Podospora anserina contribute to the enzymatic degradation of lignocellulosic biomass. In this study, P. anserina mannanases were further subjected to detailed comparative analysis of their substrate specificities, active site organization, and transglycosylation capacity. Although PaMan5A displays a classical mode of action, PaMan26A revealed an atypical hydrolysis pattern with the release of mannotetraose and mannose from mannopentaose resulting from a predominant binding mode involving the -4 subsite. The crystal structures of PaMan5A and PaMan26A were solved at 1.4 and 2.85 Å resolution, respectively. Analysis of the PaMan26A structure supported strong interaction with substrate at the -4 subsite mediated by two aromatic residues Trp-244 and Trp-245. The PaMan26A structure appended to its family 35 carbohydrate binding module revealed a short and proline-rich rigid linker that anchored together the catalytic and the binding modules.
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Affiliation(s)
- Marie Couturier
- INRA, UMR1163 BCF, Aix Marseille Université, Polytech Marseille, F-13288 Marseille, France
| | - Alain Roussel
- Architecture et Fonction des Macromolécules Biologiques, Aix Marseille Université, CNRS UMR7257, F-13288 Marseille, France
| | - Anna Rosengren
- Department of Biochemistry and Structural Biology, Lund University, P. O. Box 124, S-221 00, Lund, Sweden
| | - Philippe Leone
- Architecture et Fonction des Macromolécules Biologiques, Aix Marseille Université, CNRS UMR7257, F-13288 Marseille, France
| | - Henrik Stålbrand
- Department of Biochemistry and Structural Biology, Lund University, P. O. Box 124, S-221 00, Lund, Sweden
| | - Jean-Guy Berrin
- INRA, UMR1163 BCF, Aix Marseille Université, Polytech Marseille, F-13288 Marseille, France.
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22
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Huang JL, Bao LX, Zou HY, Che SG, Wang GX. High-level production of a cold-active B-mannanase from Bacillus subtilis Bs5 and its molecular cloning and expression. MOLECULAR GENETICS MICROBIOLOGY AND VIROLOGY 2012. [DOI: 10.3103/s0891416812040039] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Silva AJD, Gómez-Mendoza DP, Junqueira M, Domont GB, Ximenes Ferreira Filho E, de Sousa MV, Ricart CAO. Blue native-PAGE analysis of Trichoderma harzianum secretome reveals cellulases and hemicellulases working as multienzymatic complexes. Proteomics 2012; 12:2729-38. [DOI: 10.1002/pmic.201200048] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Adelson Joel da Silva
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Diana Paola Gómez-Mendoza
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Magno Junqueira
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | | | | | - Marcelo Valle de Sousa
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Carlos André Ornelas Ricart
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
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24
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Paës G, Berrin JG, Beaugrand J. GH11 xylanases: Structure/function/properties relationships and applications. Biotechnol Adv 2011; 30:564-92. [PMID: 22067746 DOI: 10.1016/j.biotechadv.2011.10.003] [Citation(s) in RCA: 281] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 10/06/2011] [Accepted: 10/13/2011] [Indexed: 01/02/2023]
Abstract
For technical, environmental and economical reasons, industrial demands for process-fitted enzymes have evolved drastically in the last decade. Therefore, continuous efforts are made in order to get insights into enzyme structure/function relationships to create improved biocatalysts. Xylanases are hemicellulolytic enzymes, which are responsible for the degradation of the heteroxylans constituting the lignocellulosic plant cell wall. Due to their variety, xylanases have been classified in glycoside hydrolase families GH5, GH8, GH10, GH11, GH30 and GH43 in the CAZy database. In this review, we focus on GH11 family, which is one of the best characterized GH families with bacterial and fungal members considered as true xylanases compared to the other families because of their high substrate specificity. Based on an exhaustive analysis of the sequences and 3D structures available so far, in relation with biochemical properties, we assess biochemical aspects of GH11 xylanases: structure, catalytic machinery, focus on their "thumb" loop of major importance in catalytic efficiency and substrate selectivity, inhibition, stability to pH and temperature. GH11 xylanases have for a long time been used as biotechnological tools in various industrial applications and represent in addition promising candidates for future other uses.
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Affiliation(s)
- Gabriel Paës
- INRA, UMR614 FARE, 2 esplanade Roland-Garros, F-51686 Reims, France.
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25
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Jin X, Meng N, Xia LM. Expression of an endo-β-1,4-glucanase gene from orpinomyces PC-2 in Pichia pastoris. Int J Mol Sci 2011; 12:3366-80. [PMID: 21686190 PMCID: PMC3116196 DOI: 10.3390/ijms12053366] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 05/03/2011] [Accepted: 05/23/2011] [Indexed: 12/03/2022] Open
Abstract
The endo-β-1,4-glucanase gene celE from the anaerobic fungus Orpinomyces PC-2 was placed under the control of an alcohol oxidase promoter (AOX1) in the plasmid pPIC9K, and integrated into the genome of a methylotrophic yeast P. pastoris GS115 by electroporation. The strain with highest endo-β-1,4-glucanase activity was selected and designed as P. pastoris egE, and cultivated in shaking flasks. The culture supernatant was assayed by SDS-polyacrylamide gel electrophoresis and showed a single band at about 52 kDa. Furthermore, the recombinant P. pastoris egE was proved to possess the ability to utilize sodium carboxymethyl cellulose as a carbon source. The recombinant endoglucanase produced by P. pastoris showed maximum activity at pH 6.0 and temperature 45 °C, indicating it was a mesophilic neutral endo-β-1,4-glucanase, suitable for denim biofinishing/washing. Further research was carried out in suitable fermentation medium in shaking flasks. The most favorable methanol addition concentration was discussed and given as 1.0%. After methanol induction for 96 h, the endo-β-1,4-glucanase activity reached 72.5 IU mL−1. This is the first report on expression and characterization of endo-β-1,4-glucanase from Orpinomyces in P. pastoris. The endo-β-1,4-glucanase secreted by recombinant P. pastoris represents an attractive potential for both academic research and textile industry application.
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Affiliation(s)
- Xin Jin
- Department of Chemical Engineering and Bioengineering, Zhejiang University, Hangzhou 310027, China; E-Mails: (X.J.); (N.M.)
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26
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Fontes CMGA, Gilbert HJ. Cellulosomes: highly efficient nanomachines designed to deconstruct plant cell wall complex carbohydrates. Annu Rev Biochem 2010; 79:655-81. [PMID: 20373916 DOI: 10.1146/annurev-biochem-091208-085603] [Citation(s) in RCA: 361] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cellulosomes can be described as one of nature's most elaborate and highly efficient nanomachines. These cell bound multienzyme complexes orchestrate the deconstruction of cellulose and hemicellulose, two of the most abundant polymers on Earth, and thus play a major role in carbon turnover. Integration of cellulosomal components occurs via highly ordered protein:protein interactions between cohesins and dockerins, whose specificity allows the incorporation of cellulases and hemicellulases onto a molecular scaffold. Cellulosome assembly promotes the exploitation of enzyme synergism because of spatial proximity and enzyme-substrate targeting. Recent structural and functional studies have revealed how cohesin-dockerin interactions mediate both cellulosome assembly and cell-surface attachment, while retaining the spatial flexibility required to optimize the catalytic synergy within the enzyme complex. These emerging advances in our knowledge of cellulosome function are reviewed here.
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Affiliation(s)
- Carlos M G A Fontes
- CIISA, Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal.
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27
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Abstract
Anaerobic chytridiomycete fungi are found in the gastrointestinal tracts of sheep, cattle and goats, as well as in many other domesticated ruminant and nonruminant herbivores and a wide variety of wild herbivorous mammals. They are principally found associated with the fibrous plant particles of digesta and as free swimming zoospores in the fluid phase. The presence of large fungal populations in animals consuming mature pasture or diets largely composed of hay or straw together with the production of highly active fibre degrading enzymes lead to' the belief that anaerobic fungi may have a significant role to play in the assimilation of fibrous feeds by ruminants. While many early studies focused on anaerobic fungi because of their unusual biology and metabolism, the large part of subsequent research has emphasized the biotechnological potential of their cellulases, xylanases and phenolic esterases. In recent years, the extent of the contribution of anaerobic fungi to the nutrition of ruminants has also been established through studies of fungal populations in the rumen and the dietary factors which influence them, as presented in this review. Further, we discuss the evidence supporting an important contribution of anaerobic fungal populations in the rumen to feed intake and digestion of poor quality feed by domesticated ruminants. In conclusion, the review explores some different methods for manipulating fungi in the rumen for increased feed intake and digestion.
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Affiliation(s)
- G L Gordon
- Commonwealth Scientific and Industrial Research Organisation, Division of Animal Production, Locked Bag 1, Delivery Centre, Blacktown, New South Wales 2148, Australia
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28
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Pai CK, Wu ZY, Chen MJ, Zeng YF, Chen JW, Duan CH, Li ML, Liu JR. Molecular cloning and characterization of a bifunctional xylanolytic enzyme from Neocallimastix patriciarum. Appl Microbiol Biotechnol 2009; 85:1451-62. [DOI: 10.1007/s00253-009-2175-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 07/29/2009] [Accepted: 07/29/2009] [Indexed: 11/24/2022]
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29
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Maki M, Leung KT, Qin W. The prospects of cellulase-producing bacteria for the bioconversion of lignocellulosic biomass. Int J Biol Sci 2009; 5:500-16. [PMID: 19680472 PMCID: PMC2726447 DOI: 10.7150/ijbs.5.500] [Citation(s) in RCA: 253] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 07/21/2009] [Indexed: 11/05/2022] Open
Abstract
Lignocellulosic biomass is a renewable and abundant resource with great potential for bioconversion to value-added bioproducts. However, the biorefining process remains economically unfeasible due to a lack of biocatalysts that can overcome costly hurdles such as cooling from high temperature, pumping of oxygen/stirring, and, neutralization from acidic or basic pH. The extreme environmental resistance of bacteria permits screening and isolation of novel cellulases to help overcome these challenges. Rapid, efficient cellulase screening techniques, using cellulase assays and metagenomic libraries, are a must. Rare cellulases with activities on soluble and crystalline cellulose have been isolated from strains of Paenibacillus and Bacillus and shown to have high thermostability and/or activity over a wide pH spectrum. While novel cellulases from strains like Cellulomonas flavigena and Terendinibacter turnerae, produce multifunctional cellulases with broader substrate utilization. These enzymes offer a framework for enhancement of cellulases including: specific activity, thermalstability, or end-product inhibition. In addition, anaerobic bacteria like the clostridia offer potential due to species capable of producing compound multienzyme complexes called cellulosomes. Cellulosomes provide synergy and close proximity of enzymes to substrate, increasing activity towards crystalline cellulose. This has lead to the construction of designer cellulosomes enhanced for specific substrate activity. Furthermore, cellulosome-producing Clostridium thermocellum and its ability to ferment sugars to ethanol; its amenability to co-culture and, recent advances in genetic engineering, offer a promising future in biofuels. The exploitation of bacteria in the search for improved enzymes or strategies provides a means to upgrade feasibility for lignocellulosic biomass conversion, ultimately providing means to a 'greener' technology.
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Affiliation(s)
- Miranda Maki
- Biorefining Research Initiative, Lakehead University, Thunder Bay, Ontario, Canada
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30
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Dhawan S, Kaur J. Microbial Mannanases: An Overview of Production and Applications. Crit Rev Biotechnol 2008; 27:197-216. [DOI: 10.1080/07388550701775919] [Citation(s) in RCA: 245] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Ljungdahl LG. The cellulase/hemicellulase system of the anaerobic fungus Orpinomyces PC-2 and aspects of its applied use. Ann N Y Acad Sci 2008; 1125:308-21. [PMID: 18378601 DOI: 10.1196/annals.1419.030] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Anaerobic fungi, first described in 1975 by Orpin, live in close contact with bacteria and other microorganisms in the rumen and caecum of herbivorous animals, where they digest ingested plant food. Seventeen distinct anaerobic fungi belonging to five different genera have been described. They have been found in at least 50 different herbivorous animals. Anaerobic fungi do not possess mitochondria, but instead have hydrogenosomes, which form hydrogen and carbon dioxide from pyruvate and malate during fermentation of carbohydrates. In addition, they are very oxygen- and temperature-sensitive, and their DNA has an unusually high AT content of from 72 to 87 mol%. My initial reason for studying anaerobic fungi was because they solubilize lignocellulose and produce all enzymes needed to efficiently hydrolyze cellulose and hemicelluloses. Although some of these enzymes are found free in the medium, most of them are associated with cellulosomal and polycellulosomal complexes, in which the enzymes are attached through fungal dockerins to scaffolding proteins; this is similar to what has been found for cellulosomes from anaerobic bacteria. Although cellulosomes from anaerobic fungi share many properties with cellulosomes of anaerobic cellulolytic bacteria and have comparable structures, their structures differ in their amino acid sequences. I discuss some features of the cellulosome of the anaerobic fungus Orpinomyces sp. PC-2 and some possible uses of its enzymes in industrial settings.
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Affiliation(s)
- Lars G Ljungdahl
- Department of Biochemistry and Molecular Biology, Fred C. Davison Life Sciences Complex, University of Georgia, Athens, GA 30602-7229, USA.
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Steenbakkers PJM, Irving JA, Harhangi HR, Swinkels WJC, Akhmanova A, Dijkerman R, Jetten MSM, van der Drift C, Whisstock JC, Op den Camp HJM. A serpin in the cellulosome of the anaerobic fungus Piromyces sp. strain E2. ACTA ACUST UNITED AC 2008; 112:999-1006. [PMID: 18539447 DOI: 10.1016/j.mycres.2008.01.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 01/08/2008] [Accepted: 01/24/2008] [Indexed: 11/17/2022]
Abstract
A gene encoding a novel component of the cellulolytic complex (cellulosome) of the anaerobic fungus Piromyces sp. strain E2 was identified. The encoded 538 amino acid protein, named celpin, consists of a signal peptide, a positively charged domain of unknown function followed by two fungal dockerins, typical for components of the extracellular fungal cellulosome. The C-terminal end consists of a 380 amino acid serine proteinase inhibitor (or serpin) domain homologue, sharing 30% identity and 50% similarity to vertebrate and bacterial serpins. Detailed protein sequence analysis of the serpin domain revealed that it contained all features of a functional serpin. It possesses the conserved amino acids present in more than 70% of known serpins, and it contained the consensus of inhibiting serpins. Because of the confined space of the fungal cellulosome inside plant tissue and the auto-proteolysis of plant material in the rumen, the fungal serpin is presumably involved in protection of the cellulosome against plant proteinases. The celpin protein of Piromyces sp. strain E2 is the first non-structural, non-hydrolytic fungal cellulosome component. Furthermore, the celpin protein of Piromyces sp. strain E2 is the first representative of a serine proteinase inhibitor of the fungal kingdom.
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Affiliation(s)
- Peter J M Steenbakkers
- Department of Microbiology, IWWR, Radboud University Nijmegen, Toernooiveld 1, NL-6525ED Nijmegen, The Netherlands
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Nagy T, Tunnicliffe RB, Higgins LD, Walters C, Gilbert HJ, Williamson MP. Characterization of a double dockerin from the cellulosome of the anaerobic fungus Piromyces equi. J Mol Biol 2007; 373:612-22. [PMID: 17869267 DOI: 10.1016/j.jmb.2007.08.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Accepted: 08/01/2007] [Indexed: 10/22/2022]
Abstract
The assembly into supramolecular complexes of proteins having complementary activities is central to cellular function. One such complex of considerable biological and industrial significance is the plant cell wall-degrading apparatus of anaerobic microorganisms, termed the cellulosome. A central feature of bacterial cellulosomes is a large non-catalytic protein, the scaffoldin, which contains multiple cohesin domains. An array of digestive enzymes is incorporated into the cellulosome through the interaction of the dockerin domains, present in the catalytic subunits, with the cohesin domains that are present in the scaffoldin. By contrast, in anaerobic fungi, such as Piromyces equi, the dockerins of cellulosomal enzymes are often present in tandem copies; however, the identity of the cognate cohesin domains in these organisms is unclear, hindering further biotechnological development of the fungal cellulosome. Here, we characterise the solution structure and function of a double-dockerin construct from the P. equi endoglucanase Cel45A. We show that the two domains are connected by a flexible linker that is short enough to keep the binding sites of the two domains on adjacent surfaces, and allows the double-dockerin construct to bind more tightly to cellulosomes than a single domain and with greater coverage. The double dockerin binds to the GH3 beta-glucosidase component of the fungal cellulosome, which is thereby identified as a potential scaffoldin.
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Affiliation(s)
- Tibor Nagy
- Institute for Cell and Molecular Biosciences, The University of Newcastle upon Tyne, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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Tsai CF, Qiu X, Liu JH. A comparative analysis of two cDNA clones of the cellulase gene family from anaerobic fungus Piromyces rhizinflata. Anaerobe 2007; 9:131-40. [PMID: 16887700 DOI: 10.1016/s1075-9964(03)00087-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Revised: 05/12/2003] [Accepted: 05/30/2003] [Indexed: 11/28/2022]
Abstract
Cellulase family and some other glycosyl hydrolases of anaerobic fungi inhabiting the digestive tract of ruminants are believed to form an enzyme complex called cellulosome. Study of the individual component of cellulosome may shed light on understanding the organization of this complex and its functional mechanism. We have analysed the primary sequences of two cellulase clones, cel5B and cel6A, isolated from the cDNA library of ruminal fungus, Piromyces rhizinflata strain 2301. The deduced amino acid sequences of the catalytic domain of Cel5B, encoded by cel5B, showed homology with the subfamily 4 of the family 5 (subfamily 5(4)) of glycosyl hydrolases, while cel6A encoded Cel6A belonged to family 6 of glycosyl hydrolases. Phylogenetic tree analysis suggested that the genes of subfamily 5(4) glycosyl hydrolases of P. rhizinflata might have been acquired from rumen bacteria. Cel5B and Cel6A were modular enzymes consisting of a catalytic domain and dockerin domain(s), but not a cellulose binding domain. The occurrence of dockerin domains indicated that both enzymes were cellulosome components. The catalytic domain of the Cel5B (Cel5B') and Cel6A (Cel6A') recombinant proteins were purified. The optimal activity conditions with carboxymethyl cellulose (CMC) as the substrate were pH 6.0 and 50 degrees C for Cel5B', and pH 6.0 and 37-45 degrees C for Cel6A'. Both Cel5B' and Cel6A' exhibited activity against CMC, barley beta-glucan, Lichenan, and oat spelt xylan. Cel5B' could also hydrolyse p-nitrophenyl-beta-d-cellobioside, Avicel and filter paper while Cel6A' did not show any activity on these substrates. It is apparent that Cel6A' acted as an endoglucanase and Cel5B' possessed both endoglucanase and exoglucanase activities. No synergic effect was observed for these recombinant enzymes in vitro on Avicel and CMC.
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Affiliation(s)
- Cheng-Fang Tsai
- Institute of BioAgricultural Sciences, Academia Sinica, Taipei, Taiwan 115, Republic of China
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Cheek S, Krishna SS, Grishin NV. Structural classification of small, disulfide-rich protein domains. J Mol Biol 2006; 359:215-37. [PMID: 16618491 DOI: 10.1016/j.jmb.2006.03.017] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 03/05/2006] [Accepted: 03/09/2006] [Indexed: 11/23/2022]
Abstract
Disulfide-rich domains are small protein domains whose global folds are stabilized primarily by the formation of disulfide bonds and, to a much lesser extent, by secondary structure and hydrophobic interactions. Disulfide-rich domains perform a wide variety of roles functioning as growth factors, toxins, enzyme inhibitors, hormones, pheromones, allergens, etc. These domains are commonly found both as independent (single-domain) proteins and as domains within larger polypeptides. Here, we present a comprehensive structural classification of approximately 3000 small, disulfide-rich protein domains. We find that these domains can be arranged into 41 fold groups on the basis of structural similarity. Our fold groups, which describe broader structural relationships than existing groupings of these domains, bring together representatives with previously unacknowledged similarities; 18 of the 41 fold groups include domains from several SCOP folds. Within the fold groups, the domains are assembled into families of homologs. We define 98 families of disulfide-rich domains, some of which include newly detected homologs, particularly among knottin-like domains. On the basis of this classification, we have examined cases of convergent and divergent evolution of functions performed by disulfide-rich proteins. Disulfide bonding patterns in these domains are also evaluated. Reducible disulfide bonding patterns are much less frequent, while symmetric disulfide bonding patterns are more common than expected from random considerations. Examples of variations in disulfide bonding patterns found within families and fold groups are discussed.
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Affiliation(s)
- Sara Cheek
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, 75390, USA
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Ximenes EA, Chen H, Kataeva IA, Cotta MA, Felix CR, Ljungdahl LG, Li XL. A mannanase, ManA, of the polycentric anaerobic fungus Orpinomyces sp. strain PC-2 has carbohydrate binding and docking modules. Can J Microbiol 2006; 51:559-68. [PMID: 16175204 PMCID: PMC6448567 DOI: 10.1139/w05-033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The anaerobic fungus Orpinomyces sp. strain PC-2 produces a broad spectrum of glycoside hydrolases, most of which are components of a high molecular mass cellulosomal complex. Here we report about a cDNA (manA) having 1924 bp isolated from the fungus and found to encode a polypeptide of 579 amino acid residues. Analysis of the deduced sequence revealed that it had a mannanase catalytic module, a family 1 carbohydrate-binding module, and a noncatalytic docking module. The catalytic module was homologous to aerobic fungal mannanases belonging to family 5 glycoside hydrolases, but unrelated to the previously isolated mannanases (family 26) of the anaerobic fungus Piromyces. No mannanase activity could be detected in Escherichia coli harboring a manA-containing plasmid. The manA was expressed in Saccharomyces cerevisiae and ManA was secreted into the culture medium in multiple forms. The purified extracellular heterologous mannanase hydrolyzed several types of mannan but lacked activity against cellulose, chitin, or beta-glucan. The enzyme had high specific activity toward locust bean mannan and an extremely broad pH profile. It was stable for several hours at 50 degrees C, but was rapidly inactivated at 60 degrees C. The carbohydrate-binding module of the Man A produced separately in E. coli bound preferably to insoluble lignocellulosic substrates, suggesting that it might play an important role in the complex enzyme system of the fungus for lignocellulose degradation.
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Affiliation(s)
- Eduardo A. Ximenes
- Laboratorio De Enzimologia, Departmento De Biologia Celular, Universidade De Brasilia, Asa Norte, Brasilia-DF-Brazil 70910-900, Brazil
| | - Huizhong Chen
- Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079-9502, USA
| | - Irina A. Kataeva
- Department of Biochemistry and Molecular Biology and Center for Biological Resource Recovery, The University of Georgia, Athens, GA 30602-7229, USA
| | - Michael A. Cotta
- Fermentation Biotechnology Research Unit, National Center for Agricultural Utilization Research, USDA/ARS, 1815 N. University Street, Peoria, IL 61604, USA
| | - Carlos R. Felix
- Laboratorio De Enzimologia, Departmento De Biologia Celular, Universidade De Brasilia, Asa Norte, Brasilia-DF-Brazil 70910-900, Brazil
| | - Lars G. Ljungdahl
- Department of Biochemistry and Molecular Biology and Center for Biological Resource Recovery, The University of Georgia, Athens, GA 30602-7229, USA
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Liu JR, Yu B, Lin SH, Cheng KJ, Chen YC. Direct cloning of a xylanase gene from the mixed genomic DNA of rumen fungi and its expression in intestinal Lactobacillus reuteri. FEMS Microbiol Lett 2006; 251:233-41. [PMID: 16146673 DOI: 10.1016/j.femsle.2005.08.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2005] [Revised: 08/04/2005] [Accepted: 08/05/2005] [Indexed: 11/30/2022] Open
Abstract
A relatively newly defined xylanase gene, xynR8, was obtained directly from a mixed DNA sample prepared from unpurified rumen fungal cultures by PCR amplification. The DNA sequence of xynR8 revealed that the gene was 884 bp in size and encoded amino acid sequences with a molecular weight of 27.9 kDa. XynR8 belonged to glycosyl hydrolase family 11, and the catalytic site residues were also found in its amino acid sequence. The main hydrolysis products of XynR8 were xylobiose, xylotriose and xylotetrose, which indicated that it belonged to the endoxylanases. The xynR8 gene was constructed so as to express and secrete under the control of the Lactococcus lactis lac A promoter and its secretion signal, and was transformed into L. reuteri Pg4, a strain isolated from the gastrointestinal tract of broiler chickens. The L. reuteri transformants harboring xynR8 not only acquired the capacity to break down xylan, but also maintained their high adhesion efficiency to mucin and mucus and their resistance to bile salts and acid.
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Affiliation(s)
- Je-Ruei Liu
- Department of Biotechnology, National Formosa University, Yunlin, Taiwan, ROC
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Huang YH, Huang CT, Hseu RS. Effects of dockerin domains onNeocallimastix frontalisxylanases. FEMS Microbiol Lett 2005; 243:455-60. [PMID: 15686849 DOI: 10.1016/j.femsle.2005.01.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Revised: 12/20/2004] [Accepted: 01/06/2005] [Indexed: 11/24/2022] Open
Abstract
Two xylanase genes were cloned from the anaerobic fungus Neocallimastix frontalis. Xyn11A had a modular structure of two catalytic domains and two dockerin domains, while Xyn11B had one catalytic domain and two dockerin domains. The characteristics of the xylanases with and without dockerin domains were investigated. The deletion of dockerin domains had little influence on the optimal pH of xylanases, while it significantly affected the optimal temperatures. The optimal temperatures increased from 55 to 60 degrees C for Xyn11A and 60 to 65 degrees C for Xyn11B after the deletion of dockerin domains. The increase of optimal temperatures was attributed to the lower stability of the second structure in full length xylanase than that in the truncated one as evidenced by the circular dichroism spectroscopy. The specific activity of Xyn11A and Xyn11B increased about 64% and 330%, respectively, after the deletion of the dockerin domains. The removal of dockerin domains appeared to increase the overall efficiency of Xyn11A' (1.2-) and Xyn11B' (2.9-) fold with oat spelts xylan as reflected by the values of k(cat)/K(m). The results suggest that the dockerin domain might play an important role in the characteristics of xylanases from anaerobic fungi.
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Affiliation(s)
- Ya-Hui Huang
- Institute of Microbiology and Biochemistry, National Taiwan University, Taipei 106, Taiwan, ROC
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Affiliation(s)
- Roy H Doi
- Section of Molecular & Cellular Biology, University of California, Davis, California, USA.
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Flint HJ. Polysaccharide Breakdown by Anaerobic Microorganisms Inhabiting the Mammalian Gut. ADVANCES IN APPLIED MICROBIOLOGY 2004; 56:89-120. [PMID: 15566977 DOI: 10.1016/s0065-2164(04)56003-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Harry J Flint
- Microbial Genetics Group Rowett Research Institute Bucksburn, Aberdeen, AB21 9SB, United Kingdom.
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Krause DO, Denman SE, Mackie RI, Morrison M, Rae AL, Attwood GT, McSweeney CS. Opportunities to improve fiber degradation in the rumen: microbiology, ecology, and genomics. FEMS Microbiol Rev 2003; 27:663-93. [PMID: 14638418 DOI: 10.1016/s0168-6445(03)00072-x] [Citation(s) in RCA: 275] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The degradation of plant cell walls by ruminants is of major economic importance in the developed as well as developing world. Rumen fermentation is unique in that efficient plant cell wall degradation relies on the cooperation between microorganisms that produce fibrolytic enzymes and the host animal that provides an anaerobic fermentation chamber. Increasing the efficiency with which the rumen microbiota degrades fiber has been the subject of extensive research for at least the last 100 years. Fiber digestion in the rumen is not optimal, as is supported by the fact that fiber recovered from feces is fermentable. This view is confirmed by the knowledge that mechanical and chemical pretreatments improve fiber degradation, as well as more recent research, which has demonstrated increased fiber digestion by rumen microorganisms when plant lignin composition is modified by genetic manipulation. Rumen microbiologists have sought to improve fiber digestion by genetic and ecological manipulation of rumen fermentation. This has been difficult and a number of constraints have limited progress, including: (a) a lack of reliable transformation systems for major fibrolytic rumen bacteria, (b) a poor understanding of ecological factors that govern persistence of fibrolytic bacteria and fungi in the rumen, (c) a poor understanding of which glycolyl hydrolases need to be manipulated, and (d) a lack of knowledge of the functional genomic framework within which fiber degradation operates. In this review the major fibrolytic organisms are briefly discussed. A more extensive discussion of the enzymes involved in fiber degradation is included. We also discuss the use of plant genetic manipulation, application of free-living lignolytic fungi and the use of exogenous enzymes. Lastly, we will discuss how newer technologies such as genomic and metagenomic approaches can be used to improve our knowledge of the functional genomic framework of plant cell wall degradation in the rumen.
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Affiliation(s)
- Denis O Krause
- CSIRO Australia, Queensland Bioscience Precinct, St. Lucia, Qld 4067, Australia.
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Harhangi HR, Akhmanova A, Steenbakkers PJM, Jetten MSM, van der Drift C, Op den Camp HJM. Genomic DNA analysis of genes encoding (hemi-)cellulolytic enzymes of the anaerobic fungus Piromyces sp. E2. Gene 2003; 314:73-80. [PMID: 14527719 DOI: 10.1016/s0378-1119(03)00705-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Anaerobic fungi contain more than one copy of genes encoding (hemi-)cellulases in their genome. The arrangement of these genes on the chromosomes was not known. A genomic DNA (gDNA) library of Piromyces sp. E2 was screened with different probes specific for (hemi-)cellulolytic enzymes. This screening resulted in three gDNA clones with genes encoding glycoside hydrolase enzymes of families 1 (beta-glucosidase), 6 (exoglucanase) and 26 (mannanase). Each clone contained two or more genes of the same family. Comparison of the gene copies on a clone revealed that they were highly homologous, and in addition, 54-75% of the substitutions was synonymous. One of the mannanase genes contained an intron. PCR with selected primers resulted in a gDNA clone with a new representative (cel9B) of glycoside hydrolase family 9 (endoglucanase). Comparison with cel9A revealed that cel9B had 67% homology on the nucleotide level. Furthermore, three introns were present. All results of this paper taken together provided evidence for duplications of (hemi-)cellulolytic genes, which resulted in clusters of almost identical genes arranged head-to-tail on the genome. In contrast to other eukaryotes, this phenomenon appears frequently in anaerobic fungi.
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Affiliation(s)
- Harry R Harhangi
- Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED, Nijmegen, The Netherlands
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Harhangi HR, Freelove ACJ, Ubhayasekera W, van Dinther M, Steenbakkers PJM, Akhmanova A, van der Drift C, Jetten MSM, Mowbray SL, Gilbert HJ, Op den Camp HJM. Cel6A, a major exoglucanase from the cellulosome of the anaerobic fungi Piromyces sp. E2 and Piromyces equi. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1628:30-9. [PMID: 12850270 DOI: 10.1016/s0167-4781(03)00112-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Anaerobic fungi possess high cellulolytic activities, which are organised in high molecular mass (HMM) complexes. Besides catalytic modules, the cellulolytic enzyme components of these complexes contain non-catalytic modules, known as dockerins, that play a key role in complex assembly. Screening of a genomic and a cDNA library of two Piromyces species resulted in the isolation of two clones containing inserts of 5.5 kb (Piromyces sp. E2) and 1.5 kb (Piromyces equi). Both clones contained the complete coding region of a glycoside hydrolase (GH) from family 6, consisting of a 20 amino acid signal peptide, a 76 (sp. E2)/81 (P. equi) amino acid stretch comprising two fungal non-catalytic docking domains (NCDDs), a 24 (sp. E2)/16 (P. equi) amino acid linker, and a 369 amino acid catalytic module. Homology modelling of the catalytic module strongly suggests that the Piromyces enzymes will be processive cellobiohydrolases. The catalytic residues and all nearby residues are conserved. The reaction is thus expected to proceed via a classical single-displacement (inverting) mechanism that is characteristic of this family of GHs. The enzyme, defined as Cel6A, encoded by the full-length Piromyces E2 sequence was expressed in Escherichia coli. The recombinant protein expressed had a molecular mass of 55 kDa and showed activity against Avicel, supporting the observed relationship of the sequence to those of known cellobiohydrolases. Affinity-purified cellulosomes of Piromyces sp. E2 were analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) electrophoresis. A major band was detected with the molecular weight of Cel6A. A tryptic fingerprint of this protein confirmed its identity.
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Affiliation(s)
- Harry R Harhangi
- Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED, Nijmegen, The Netherlands
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Steenbakkers PJM, Harhangi HR, Bosscher MW, van der Hooft MMC, Keltjens JT, van der Drift C, Vogels GD, op den Camp HJM. beta-Glucosidase in cellulosome of the anaerobic fungus Piromyces sp. strain E2 is a family 3 glycoside hydrolase. Biochem J 2003; 370:963-70. [PMID: 12485115 PMCID: PMC1223235 DOI: 10.1042/bj20021767] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Revised: 12/13/2002] [Accepted: 12/16/2002] [Indexed: 11/17/2022]
Abstract
The cellulosomes of anaerobic fungi convert crystalline cellulose solely into glucose, in contrast with bacterial cellulosomes which produce cellobiose. Previously, a beta-glucosidase was identified in the cellulosome of Piromyces sp. strain E2 by zymogram analysis, which represented approx. 25% of the extracellular beta-glucosidase activity. To identify the component in the fungal cellulosome responsible for the beta-glucosidase activity, immunoscreening with anti-cellulosome antibodies was used to isolate the corresponding gene. A 2737 bp immunoclone was isolated from a cDNA library. The clone encoded an extracellular protein containing a eukaryotic family 3 glycoside hydrolase domain homologue and was therefore named cel3A. The C-terminal end of the encoded Cel3A protein consisted of an auxiliary domain and three fungal dockerins, typical for cellulosome components. The Cel3A catalytic domain was expressed in Escherichia coli BL21 and purified. Biochemical analyses of the recombinant protein showed that the Cel3A catalytic domain was specific for beta-glucosidic bonds and functioned as an exoglucohydrolase on soluble substrates as well as cellulose. Comparison of the apparent K (m) and K (i) values of heterologous Cel3A and the fungal cellulosome for p -nitrophenyl-beta-D-glucopyranoside and D-glucono-1,5-delta-lactone respectively indicated that cel3A encodes the beta-glucosidase activity of the Piromyces sp. strain E2 cellulosome.
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Affiliation(s)
- Peter J M Steenbakkers
- Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands
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Rincon MT, Ding SY, McCrae SI, Martin JC, Aurilia V, Lamed R, Shoham Y, Bayer EA, Flint HJ. Novel organization and divergent dockerin specificities in the cellulosome system of Ruminococcus flavefaciens. J Bacteriol 2003; 185:703-13. [PMID: 12533446 PMCID: PMC142803 DOI: 10.1128/jb.185.3.703-713.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2002] [Accepted: 09/30/2002] [Indexed: 11/20/2022] Open
Abstract
The DNA sequence coding for putative cellulosomal scaffolding protein ScaA from the rumen cellulolytic anaerobe Ruminococcus flavefaciens 17 was completed. The mature protein exhibits a calculated molecular mass of 90,198 Da and comprises three cohesin domains, a C-terminal dockerin, and a unique N-terminal X domain of unknown function. A novel feature of ScaA is the absence of an identifiable cellulose-binding module. Nevertheless, native ScaA was detected among proteins that attach to cellulose and appeared as a glycosylated band migrating at around 130 kDa. The ScaA dockerin was previously shown to interact with the cohesin-containing putative surface-anchoring protein ScaB. Here, six of the seven cohesins from ScaB were overexpressed as histidine-tagged products in E. coli; despite their considerable sequence differences, each ScaB cohesin specifically recognized the native 130-kDa ScaA protein. The binding specificities of dockerins found in R. flavefaciens plant cell wall-degrading enzymes were examined next. The dockerin sequences of the enzymes EndA, EndB, XynB, and XynD are all closely related but differ from those of XynE and CesA. A recombinant ScaA cohesin bound selectively to dockerin-containing fragments of EndB, but not to those of XynE or CesA. Furthermore, dockerin-containing EndB and XynB, but not XynE or CesA, constructs bound specifically to native ScaA. XynE- and CesA-derived probes did however bind a number of alternative R. flavefaciens bands, including an approximately 110-kDa supernatant protein expressed selectively in cultures grown on xylan. Our findings indicate that in addition to the ScaA dockerin-ScaB cohesin interaction, at least two distinct dockerin-binding specificities are involved in the novel organization of plant cell wall-degrading enzymes in this species and suggest that different scaffoldins and perhaps multiple enzyme complexes may exist in R. flavefaciens.
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Affiliation(s)
- Marco T Rincon
- Gut Microbiology Group, Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, United Kingdom
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Charnock SJ, Bolam DN, Nurizzo D, Szabó L, McKie VA, Gilbert HJ, Davies GJ. Promiscuity in ligand-binding: The three-dimensional structure of a Piromyces carbohydrate-binding module, CBM29-2, in complex with cello- and mannohexaose. Proc Natl Acad Sci U S A 2002; 99:14077-82. [PMID: 12391332 PMCID: PMC137839 DOI: 10.1073/pnas.212516199] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2002] [Accepted: 08/26/2002] [Indexed: 11/18/2022] Open
Abstract
Carbohydrate-protein recognition is central to many biological processes. Enzymes that act on polysaccharide substrates frequently contain noncatalytic domains, "carbohydrate-binding modules" (CBMs), that target the enzyme to the appropriate substrate. CBMs that recognize specific plant structural polysaccharides are often able to accommodate both the variable backbone and the side-chain decorations of heterogeneous ligands. "CBM29" modules, derived from a noncatalytic component of the Piromyces equi cellulase/hemicellulase complex, provide an example of this selective yet flexible recognition. They discriminate strongly against some polysaccharides while remaining relatively promiscuous toward both beta-1,4-linked manno- and cello-oligosaccharides. This feature may reflect preferential, but flexible, targeting toward glucomannans in the plant cell wall. The three-dimensional structure of CBM29-2 and its complexes with cello- and mannohexaose reveal a beta-jelly-roll topology, with an extended binding groove on the concave surface. The orientation of the aromatic residues complements the conformation of the target sugar polymer while accommodation of both manno- and gluco-configured oligo- and polysaccharides is conferred by virtue of the plasticity of the direct interactions from their axial and equatorial 2-hydroxyls, respectively. Such flexible ligand recognition targets the anaerobic fungal complex to a range of different components in the plant cell wall and thus plays a pivotal role in the highly efficient degradation of this composite structure by the microbial eukaryote.
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Affiliation(s)
- Simon J Charnock
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, United Kingdom
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Lynd LR, Weimer PJ, van Zyl WH, Pretorius IS. Microbial cellulose utilization: fundamentals and biotechnology. Microbiol Mol Biol Rev 2002; 66:506-77, table of contents. [PMID: 12209002 PMCID: PMC120791 DOI: 10.1128/mmbr.66.3.506-577.2002] [Citation(s) in RCA: 2307] [Impact Index Per Article: 104.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
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Affiliation(s)
- Lee R Lynd
- Chemical and Biochemical Engineering, Thayer School of Engineering and Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
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48
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Steenbakkers PJM, Ubhayasekera W, Goossen HJAM, van Lierop EMHM, van der Drift C, Vogels GD, Mowbray SL, Op den Camp HJM. An intron-containing glycoside hydrolase family 9 cellulase gene encodes the dominant 90 kDa component of the cellulosome of the anaerobic fungus Piromyces sp. strain E2. Biochem J 2002; 365:193-204. [PMID: 12071852 PMCID: PMC1222669 DOI: 10.1042/bj20011866] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The cellulosome produced by Piromyces sp. strain E2 during growth on filter paper was purified by using an optimized cellulose-affinity method consisting of steps of EDTA washing of the cellulose-bound protein followed by elution with water. Three dominant proteins were identified in the cellulosome preparation, with molecular masses of 55, 80 and 90 kDa. Treatment of cellulose-bound cellulosome with a number of denaturing agents was also tested. Incubation with 0.5% (w/v) SDS or 8 M urea released most cellulosomal proteins, while leaving the greater fraction of the 80, 90 and 170 kDa components. To investigate the major 90 kDa cellulosome protein further, the corresponding gene, cel9A, was isolated, using immunoscreening and N-terminal sequencing. Inspection of the cel9A genomic organization revealed the presence of four introns, allowing the construction of a consensus for introns in anaerobic fungi. The 2800 bp cDNA clone contained an open reading frame of 2334 bp encoding a 757-residue extracellular protein. Cel9A includes a 445-residue glycoside hydrolase family 9 catalytic domain, and so is the first fungal representative of this large family. Both modelling of the catalytic domain as well as the activity measured with low level expression in Escherichia coli indicated that Cel9A is an endoglucanase. The catalytic domain is succeeded by a putative beta-sheet module of 160 amino acids with unknown function, followed by a threonine-rich linker and three fungal docking domains. Homology modelling of the Cel9A dockerins suggested that the cysteine residues present are all involved in disulphide bridges. The results presented here are used to discuss evolution of glycoside hydrolase family 9 enzymes.
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Affiliation(s)
- Peter J M Steenbakkers
- Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands
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Voncken F, Boxma B, Tjaden J, Akhmanova A, Huynen M, Verbeek F, Tielens AGM, Haferkamp I, Neuhaus HE, Vogels G, Veenhuis M, Hackstein JHP. Multiple origins of hydrogenosomes: functional and phylogenetic evidence from the ADP/ATP carrier of the anaerobic chytrid Neocallimastix sp. Mol Microbiol 2002; 44:1441-54. [PMID: 12067335 DOI: 10.1046/j.1365-2958.2002.02959.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A mitochondrial-type ADP/ATP carrier (AAC) has been identified in the hydrogenosomes of the anaerobic chytridiomycete fungus Neocallimastix sp. L2. Biochemical and immunocytochemical studies revealed that this ADP/ATP carrier is an integral component of hydrogenosomal membranes. Expression of the corresponding cDNA in Escherichia coli confers the ability on the bacterial host to incorporate ADP at significantly higher rates than ATP--similar to isolated mitochondria of yeast and animals. Phylogenetic analysis of this AAC gene (hdgaac) confirmed with high statistical support that the hydrogenosomal ADP/ATP carrier of Neocallimastix sp. L2 belongs to the family of veritable mitochondrial-type AACs. Hydrogenosome-bearing anaerobic ciliates possess clearly distinct mitochondrial-type AACs, whereas the potential hydrogenosomal carrier Hmp31 of the anaerobic flagellate Trichomonas vaginalis and its homologue from Trichomonas gallinae do not belong to this family of proteins. Also, phylogenetic analysis of genes encoding mitochondrial-type chaperonin 60 proteins (HSP 60) supports the conclusion that the hydrogenosomes of anaerobic chytrids and anaerobic ciliates had independent origins, although both of them arose from mitochondria.
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Affiliation(s)
- Frank Voncken
- Department of Evolutionary Microbiology, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands
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Sapag A, Wouters J, Lambert C, de Ioannes P, Eyzaguirre J, Depiereux E. The endoxylanases from family 11: computer analysis of protein sequences reveals important structural and phylogenetic relationships. J Biotechnol 2002; 95:109-31. [PMID: 11911922 DOI: 10.1016/s0168-1656(02)00002-0] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Eighty-two amino acid sequences of the catalytic domains of mature endoxylanases belonging to family 11 have been aligned using the programs MATCHBOX and CLUSTAL. The sequences range in length from 175 to 233 residues. The two glutamates acting as catalytic residues are conserved in all sequences. A very good correlation is found between the presence (at position 100) of an asparagine in the so-called 'alkaline' xylanases, or an aspartic acid in those with a more acidic pH optimum. Four boxes defining segments of highest similarity were detected; they correspond to regions of defined secondary structure: B5, B6, B8 and the carboxyl end of the alpha helix, respectively. Cysteine residues are not common in these sequences (0.7% of all residues), and disulfide bridges are not important in explaining the stability of several thermophilic xylanases. The alignment allows the classification of the enzymes in groups according to sequence similarity. Fungal and bacterial enzymes were found to form mostly separate clusters of higher similarity.
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Affiliation(s)
- Amalia Sapag
- Laboratorio de Bioquímica, Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
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