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Insights into exo- and endoglucanase activities of family 6 glycoside hydrolases from Podospora anserina. Appl Environ Microbiol 2013; 79:4220-9. [PMID: 23645193 DOI: 10.1128/aem.00327-13] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The ascomycete Podospora anserina is a coprophilous fungus that grows at late stages on droppings of herbivores. Its genome encodes a large diversity of carbohydrate-active enzymes. Among them, four genes encode glycoside hydrolases from family 6 (GH6), the members of which comprise putative endoglucanases and exoglucanases, some of them exerting important functions for biomass degradation in fungi. Therefore, this family was selected for functional analysis. Three of the enzymes, P. anserina Cel6A (PaCel6A), PaCel6B, and PaCel6C, were functionally expressed in the yeast Pichia pastoris. All three GH6 enzymes hydrolyzed crystalline and amorphous cellulose but were inactive on hydroxyethyl cellulose, mannan, galactomannan, xyloglucan, arabinoxylan, arabinan, xylan, and pectin. PaCel6A had a catalytic efficiency on cellotetraose comparable to that of Trichoderma reesei Cel6A (TrCel6A), but PaCel6B and PaCel6C were clearly less efficient. PaCel6A was the enzyme with the highest stability at 45°C, while PaCel6C was the least stable enzyme, losing more than 50% of its activity after incubation at temperatures above 30°C for 24 h. In contrast to TrCel6A, all three studied P. anserina GH6 cellulases were stable over a wide range of pHs and conserved high activity at pH values of up to 9. Each enzyme displayed a distinct substrate and product profile, highlighting different modes of action, with PaCel6A being the enzyme most similar to TrCel6A. PaCel6B was the only enzyme with higher specific activity on carboxymethylcellulose (CMC) than on Avicel and showed lower processivity than the others. Structural modeling predicts an open catalytic cleft, suggesting that PaCel6B is an endoglucanase.
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52
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Bubner P, Plank H, Nidetzky B. Visualizing cellulase activity. Biotechnol Bioeng 2013; 110:1529-49. [DOI: 10.1002/bit.24884] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 01/08/2013] [Accepted: 02/22/2013] [Indexed: 11/08/2022]
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53
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Bu L, Crowley MF, Himmel ME, Beckham GT. Computational investigation of the pH dependence of loop flexibility and catalytic function in glycoside hydrolases. J Biol Chem 2013; 288:12175-86. [PMID: 23504310 DOI: 10.1074/jbc.m113.462465] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellulase enzymes cleave glycosidic bonds in cellulose to produce cellobiose via either retaining or inverting hydrolysis mechanisms, which are significantly pH-dependent. Many fungal cellulases function optimally at pH ~5, and their activities decrease dramatically at higher or lower pH. To understand the molecular-level implications of pH in cellulase structure, we use a hybrid, solvent-based, constant pH molecular dynamics method combined with pH-based replica exchange to determine the pK(a) values of titratable residues of a glycoside hydrolase (GH) family 6 cellobiohydrolase (Cel6A) and a GH family 7 cellobiohydrolase (Cel7A) from the fungus Hypocrea jecorina. For both enzymes, we demonstrate that a bound substrate significantly affects the pKa values of the acid residues at the catalytic center. The calculated pK(a) values of catalytic residues confirm their proposed roles from structural studies and are consistent with the experimentally measured apparent pKa values. Additionally, GHs are known to impart a strained pucker conformation in carbohydrate substrates in active sites for catalysis, and results from free energy calculations combined with constant pH molecular dynamics suggest that the correct ring pucker is stable near the optimal pH for both Cel6A and Cel7A. Much longer molecular dynamics simulations of Cel6A and Cel7A with fixed protonation states based on the calculated pK(a) values suggest that pH affects the flexibility of tunnel loops, which likely affects processivity and substrate complexation. Taken together, this work demonstrates several molecular-level effects of pH on GH enzymes important for cellulose turnover in the biosphere and relevant to biomass conversion processes.
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Affiliation(s)
- Lintao Bu
- National Bioenergy Center, Colorado School of Mines, Golden, Colorado 80401, USA.
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Valo H, Arola S, Laaksonen P, Torkkeli M, Peltonen L, Linder MB, Serimaa R, Kuga S, Hirvonen J, Laaksonen T. Drug release from nanoparticles embedded in four different nanofibrillar cellulose aerogels. Eur J Pharm Sci 2013; 50:69-77. [PMID: 23500041 DOI: 10.1016/j.ejps.2013.02.023] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 12/20/2012] [Accepted: 02/27/2013] [Indexed: 11/27/2022]
Abstract
Highly porous nanocellulose aerogels prepared by freeze-drying from various nanofibrillar cellulose (NFC) hydrogels are introduced as nanoparticle reservoirs for oral drug delivery systems. Here we show that beclomethasone dipropionate (BDP) nanoparticles coated with amphiphilic hydrophobin proteins can be well integrated into the NFC aerogels. NFCs from four different origins are introduced and compared to microcrystalline cellulose (MCC). The nanocellulose aerogel scaffolds made from red pepper (RC) and MCC release the drug immediately, while bacterial cellulose (BC), quince seed (QC) and TEMPO-oxidized birch cellulose-based (TC) aerogels show sustained drug release. Since the release of the drug is controlled by the structure and interactions between the nanoparticles and the cellulose matrix, modulation of the matrix formers enable a control of the drug release rate. These nanocomposite structures can be very useful in many pharmaceutical nanoparticle applications and open up new possibilities as carriers for controlled drug delivery.
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Affiliation(s)
- Hanna Valo
- Division of Pharmaceutical Technology, Faculty of Pharmacy, University of Helsinki, PO Box 56, FIN-00014 Helsinki, Finland
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55
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Gaikwad A, Chakraborty S. Mixing Effects on the Kinetics of Enzymatic Hydrolysis of Avicel for Batch Production of Cellulosic Ethanol. Ind Eng Chem Res 2013. [DOI: 10.1021/ie301234b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ashwin Gaikwad
- Department of Chemical
Engineering, Indian Institute of Technology − Kharagpur, Kharagpur
721302, India
| | - Saikat Chakraborty
- Department of Chemical
Engineering, Indian Institute of Technology − Kharagpur, Kharagpur
721302, India
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56
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Wu I, Arnold FH. Engineered thermostable fungal Cel6A and Cel7A cellobiohydrolases hydrolyze cellulose efficiently at elevated temperatures. Biotechnol Bioeng 2013; 110:1874-83. [PMID: 23404363 DOI: 10.1002/bit.24864] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Revised: 01/21/2013] [Accepted: 01/28/2013] [Indexed: 11/05/2022]
Abstract
Thermostability is an important feature in industrial enzymes: it increases biocatalyst lifetime and enables reactions at higher temperatures, where faster rates and other advantages ultimately reduce the cost of biocatalysis. Here we report the thermostabilization of a chimeric fungal family 6 cellobiohydrolase (HJPlus) by directed evolution using random mutagenesis and recombination of beneficial mutations. Thermostable variant 3C6P has a half-life of 280 min at 75°C and a T(50) of 80.1°C, a ~15°C increase over the thermostable Cel6A from Humicola insolens (HiCel6A) and a ~20°C increase over that from Hypocrea jecorina (HjCel6A). Most of the mutations also stabilize the less-stable HjCel6A, the wild-type Cel6A closest in sequence to 3C6P. During a 60-h Avicel hydrolysis, 3C6P released 2.4 times more cellobiose equivalents at its optimum temperature (T(opt)) of 75°C than HiCel6A at its T(opt) of 60°C. The total cellobiose equivalents released by HiCel6A at 60°C after 60 h is equivalent to the total released by 3C6P at 75°C after ~6 h, a 10-fold reduction in hydrolysis time. A binary mixture of thermostable Cel6A and Cel7A hydrolyzes Avicel synergistically and released 1.8 times more cellobiose equivalents than the wild-type mixture, both mixtures assessed at their respective T(opt). Crystal structures of HJPlus and 3C6P, determined at 1.5 and 1.2 Å resolution, indicate that the stabilization comes from improved hydrophobic interactions and restricted loop conformations by introduced proline residues.
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Affiliation(s)
- Indira Wu
- Division of Chemistry and Chemical Engineering, California Institute of Technology 210-41, Pasadena, CA 91125, USA
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57
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Illustration of the development of bacterial cellulose bundles/ribbons by Gluconacetobacter xylinus via atomic force microscopy. Appl Microbiol Biotechnol 2013; 97:4353-9. [DOI: 10.1007/s00253-013-4752-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 01/29/2013] [Accepted: 01/31/2013] [Indexed: 02/08/2023]
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58
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Sandgren M, Wu M, Karkehabadi S, Mitchinson C, Kelemen BR, Larenas EA, Ståhlberg J, Hansson H. The Structure of a Bacterial Cellobiohydrolase: The Catalytic Core of the Thermobifida fusca Family GH6 Cellobiohydrolase Cel6B. J Mol Biol 2013; 425:622-35. [DOI: 10.1016/j.jmb.2012.11.039] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/26/2012] [Accepted: 11/28/2012] [Indexed: 10/27/2022]
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59
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Momeni MH, Payne CM, Hansson H, Mikkelsen NE, Svedberg J, Engström Å, Sandgren M, Beckham GT, Ståhlberg J. Structural, biochemical, and computational characterization of the glycoside hydrolase family 7 cellobiohydrolase of the tree-killing fungus Heterobasidion irregulare. J Biol Chem 2013; 288:5861-72. [PMID: 23303184 DOI: 10.1074/jbc.m112.440891] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Root rot fungi of the Heterobasidion annosum complex are the most damaging pathogens in temperate forests, and the recently sequenced Heterobasidion irregulare genome revealed over 280 carbohydrate-active enzymes. Here, H. irregulare was grown on biomass, and the most abundant protein in the culture filtrate was identified as the only family 7 glycoside hydrolase in the genome, which consists of a single catalytic domain, lacking a linker and carbohydrate-binding module. The enzyme, HirCel7A, was characterized biochemically to determine the optimal conditions for activity. HirCel7A was crystallized and the structure, refined at 1.7 Å resolution, confirms that HirCel7A is a cellobiohydrolase rather than an endoglucanase, with a cellulose-binding tunnel that is more closed than Phanerochaete chrysosporium Cel7D and more open than Hypocrea jecorina Cel7A, suggesting intermediate enzyme properties. Molecular simulations were conducted to ascertain differences in enzyme-ligand interactions, ligand solvation, and loop flexibility between the family 7 glycoside hydrolase cellobiohydrolases from H. irregulare, H. jecorina, and P. chrysosporium. The structural comparisons and simulations suggest significant differences in enzyme-ligand interactions at the tunnel entrance in the -7 to -4 binding sites and suggest that a tyrosine residue at the tunnel entrance of HirCel7A may serve as an additional ligand-binding site. Additionally, the loops over the active site in H. jecorina Cel7A are more closed than loops in the other two enzymes, which has implications for the degree of processivity, endo-initiation, and substrate dissociation. Overall, this study highlights molecular level features important to understanding this biologically and industrially important family of glycoside hydrolases.
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Affiliation(s)
- Majid Haddad Momeni
- Department of Molecular Biology, Swedish University of Agricultural Sciences, SE-751 24 Uppsala, Sweden
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60
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Wu M, Nerinckx W, Piens K, Ishida T, Hansson H, Sandgren M, Ståhlberg J. Rational design, synthesis, evaluation and enzyme-substrate structures of improved fluorogenic substrates for family 6 glycoside hydrolases. FEBS J 2012; 280:184-98. [DOI: 10.1111/febs.12060] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 10/31/2012] [Accepted: 11/05/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Miao Wu
- Department of Molecular Biology; Swedish University of Agricultural Sciences; Uppsala; Sweden
| | - Wim Nerinckx
- Laboratory for Protein Biochemistry and Biomolecular Engineering; Department of Biochemistry and Microbiology; University of Gent; Gent; Belgium
| | | | - Takuya Ishida
- Department of Molecular Biology; Swedish University of Agricultural Sciences; Uppsala; Sweden
| | - Henrik Hansson
- Department of Molecular Biology; Swedish University of Agricultural Sciences; Uppsala; Sweden
| | - Mats Sandgren
- Department of Molecular Biology; Swedish University of Agricultural Sciences; Uppsala; Sweden
| | - Jerry Ståhlberg
- Department of Molecular Biology; Swedish University of Agricultural Sciences; Uppsala; Sweden
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61
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Redefining XynA from Penicillium funiculosum IMI 378536 as a GH7 cellobiohydrolase. ACTA ACUST UNITED AC 2012; 39:1569-76. [DOI: 10.1007/s10295-012-1166-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 06/19/2012] [Indexed: 10/28/2022]
Abstract
Abstract
The secretome of Penicillium funiculosum contains two family GH7 enzymes, one of which (designated XynA) has been described as a xylanase. This is unusual because it is the only xylanase in family GH7, which is mainly composed of cellobiohydrolases and endoglucanases, and also because XynA is highly similar to the cellobiohydrolase I from Talaromyces emersonii and Trichoderma reesei (72 and 65 % identity, respectively). To probe this enigma, we investigated the biochemical properties of XynA, notably its activity on xylans and β-d-glucans. A highly pure sample of XynA was obtained and used to perform hydrolysis tests on polysaccharides. These revealed that XynA is 100-fold more active on β-1,4-glucan than on xylan. Likewise, XynA was active on both 4-nitrophenyl-β-d-lactopyranoside (pNP-β-d-Lac) and 4-nitrophenyl-β-d-cellobioside (pNP-cellobiose), which shows that XynA is principally an exo-acting type 1 cellobiohydrolase enzyme that displays 5.2-fold higher performance on pNP-cellobiose than on pNP-β-d-Lac. Finally, analyses performed using cellodextrins as substrate revealed that XynA mainly produced cellobiose (C2) from substrates containing three or more glucosyl subunits, and that C2 inhibits XynA at high concentrations (IC50 C2 = 17.7 μM). Overall, this study revealed that XynA displays typical cellobiohydrolase 1 activity and confirms that the description of this enzyme in public databases should be definitively amended. Moreover, the data provided here complete the information provided by a previous proteomics investigation and reveal that P. funiculosum secretes a complete set of cellulose-degrading enzymes.
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62
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Ganner T, Bubner P, Eibinger M, Mayrhofer C, Plank H, Nidetzky B. Dissecting and reconstructing synergism: in situ visualization of cooperativity among cellulases. J Biol Chem 2012; 287:43215-22. [PMID: 23118223 PMCID: PMC3527909 DOI: 10.1074/jbc.m112.419952] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellulose is the most abundant biopolymer and a major reservoir of fixed carbon on earth. Comprehension of the elusive mechanism of its enzymatic degradation represents a fundamental problem at the interface of biology, biotechnology, and materials science. The interdependence of cellulose disintegration and hydrolysis and the synergistic interplay among cellulases is yet poorly understood. Here we report evidence from in situ atomic force microscopy (AFM) that delineates degradation of a polymorphic cellulose substrate as a dynamic cycle of alternating exposure and removal of crystalline fibers. Direct observation shows that chain-end-cleaving cellobiohydrolases (CBH I, CBH II) and an internally chain-cleaving endoglucanase (EG), the major components of cellulase systems, take on distinct roles: EG and CBH II make the cellulose surface accessible for CBH I by removing amorphous-unordered substrate areas, thus exposing otherwise embedded crystalline-ordered nanofibrils of the cellulose. Subsequently, these fibrils are degraded efficiently by CBH I, thereby uncovering new amorphous areas. Without prior action of EG and CBH II, CBH I was poorly active on the cellulosic substrate. This leads to the conclusion that synergism among cellulases is morphology-dependent and governed by the cooperativity between enzymes degrading amorphous regions and those targeting primarily crystalline regions. The surface-disrupting activity of cellulases therefore strongly depends on mesoscopic structural features of the substrate: size and packing of crystalline fibers are key determinants of the overall efficiency of cellulose degradation.
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Affiliation(s)
- Thomas Ganner
- Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
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63
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Moraïs S, Barak Y, Lamed R, Wilson DB, Xu Q, Himmel ME, Bayer EA. Paradigmatic status of an endo- and exoglucanase and its effect on crystalline cellulose degradation. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:78. [PMID: 23095278 PMCID: PMC3502487 DOI: 10.1186/1754-6834-5-78] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/19/2012] [Indexed: 05/07/2023]
Abstract
BACKGROUND Microorganisms employ a multiplicity of enzymes to efficiently degrade the composite structure of plant cell wall cellulosic polysaccharides. These remarkable enzyme systems include glycoside hydrolases (cellulases, hemicellulases), polysaccharide lyases, and the carbohydrate esterases. To accomplish this challenging task, several strategies are commonly observed either separately or in combination. These include free enzyme systems, multifunctional enzymes, and multi-enzyme self-assembled designer cellulosome complexes. RESULTS In order to compare these different paradigms, we employed a synthetic biology approach to convert two different cellulases from the free enzymatic system of the well-studied bacterium, Thermobifida fusca, into bifunctional enzymes with different modular architectures. We then examined their performance compared to those of the combined parental free-enzyme and equivalent designer-cellulosome systems. The results showed that the cellulolytic activity displayed by the different architectures of the bifunctional enzymes was somewhat inferior to that of the wild-type free enzyme system. CONCLUSIONS The activity exhibited by the designer cellulosome system was equal or superior to that of the free system, presumably reflecting the combined proximity of the enzymes and high flexibility of the designer cellulosome components, thus enabling efficient enzymatic activity of the catalytic modules.
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Affiliation(s)
- Sarah Moraïs
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
- Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel
| | - Yoav Barak
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
- Chemical Research Support, The Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, 69978, Israel
| | - David B Wilson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Qi Xu
- Biosciences Center, National Renewable Energy Laboratory (NREL) and BioEnergy Science Center (BESC), Golden, CO, USA
| | - Michael E Himmel
- Biosciences Center, National Renewable Energy Laboratory (NREL) and BioEnergy Science Center (BESC), Golden, CO, USA
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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64
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Heterologous expression of cellobiohydrolase II (Cel6A) in maize endosperm. Transgenic Res 2012; 22:477-88. [PMID: 23080294 DOI: 10.1007/s11248-012-9659-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
Abstract
The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing.
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65
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Oliveira GS, Ulhoa CJ, Silveira MHL, Andreaus J, Silva-Pereira I, Poças-Fonseca MJ, Faria FP. An alkaline thermostable recombinant Humicola grisea var. thermoidea cellobiohydrolase presents bifunctional (endo/exoglucanase) activity on cellulosic substrates. World J Microbiol Biotechnol 2012; 29:19-26. [PMID: 23054694 DOI: 10.1007/s11274-012-1153-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 08/09/2012] [Indexed: 11/25/2022]
Abstract
Humicola grisea var. thermoidea is a deuteromycete which secretes a large spectrum of hydrolytic enzymes when grown on lignocellulosic residues. This study focused on the heterologous expression and recombinant enzyme analysis of the major secreted cellulase when the fungus is grown on sugarcane bagasse as the sole carbon source. Cellobiohydrolase 1.2 (CBH 1.2) cDNA was cloned in Pichia pastoris under control of the AOX1 promoter. Recombinant protein (rCBH1.2) was efficiently produced and secreted as a functional enzyme, presenting a molecular mass of 47 kDa. Maximum enzyme production was achieved at 96 h, in culture medium supplemented with 1.34 % urea and 1 % yeast extract and upon induction with 1 % methanol. Recombinant enzyme exhibited optimum activity at 60 °C and pH 8, and presented a remarkable thermostability, particularly at alkaline pH. Activity was evaluated on different cellulosic substrates (carboxymethyl cellulose, filter paper, microcrystalline cellulose and 4-para-nitrophenyl β-D-glucopyranoside). Interestingly, rCBH1.2 presented both exoglucanase and endoglucanase activities and mechanical agitation increased substrate hydrolysis. Results indicate that rCBH1.2 is a potential biocatalyst for applications in the textile industry or detergent formulation.
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Affiliation(s)
- G S Oliveira
- Laboratório de Biotecnologia de Fungos, Departamento de Bioquímica e Biologia Molecular, Instituto de Ciências Biológicas, Campus II, Universidade Federal de Goiás, Goiânia, GO, CEP: 74001-970, Brazil
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66
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Taneda D, Ueno Y, Ikeo M, Okino S. Characteristics of enzyme hydrolysis of cellulose under static condition. BIORESOURCE TECHNOLOGY 2012; 121:154-60. [PMID: 22858480 DOI: 10.1016/j.biortech.2012.06.104] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 06/26/2012] [Accepted: 06/28/2012] [Indexed: 05/14/2023]
Abstract
The effect of enzyme loading under static and agitated conditions was investigated. Enzymatic hydrolysis of 10 w/v% de-lignified cellulose slurry such as filter paper, avicel and pulp was conducted under agitated (120 rpm) and static condition, and the enzyme loading ranging from 1.2 to 120 mg-protein/g-dry substrate. Under the agitated condition, the final sugar concentration decreased with the decreasing enzyme loading. Under the static condition, the final sugar concentration was maintained even if the enzyme loading was decreased. The above phenomenon was caused by a rapid precipitation of cellobiohydrolase 2 (CBH2) under the agitated condition, which was not observed under the static condition. The hydrolysis experiments using enzymes containing different ratios of cellobiohydrolase 1 (CBH1) and CBH2 under the static condition suggested that preservation of CBH2 and its synergism with CBH1 is essential for static condition's characteristics, and for efficient hydrolysis of cellulose.
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Affiliation(s)
- Daisuke Taneda
- JGC Corporation, 2205, Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Pref., 311-1313, Japan.
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67
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Thompson AJ, Heu T, Shaghasi T, Benyamino R, Jones A, Friis EP, Wilson KS, Davies GJ. Structure of the catalytic core module of theChaetomium thermophilumfamily GH6 cellobiohydrolase Cel6A. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:875-82. [DOI: 10.1107/s0907444912016496] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 04/16/2012] [Indexed: 11/11/2022]
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68
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Bu L, Nimlos MR, Shirts MR, Ståhlberg J, Himmel ME, Crowley MF, Beckham GT. Product binding varies dramatically between processive and nonprocessive cellulase enzymes. J Biol Chem 2012; 287:24807-13. [PMID: 22648408 DOI: 10.1074/jbc.m112.365510] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellulases hydrolyze β-1,4 glycosidic linkages in cellulose, which are among the most prevalent and stable bonds in Nature. Cellulases comprise many glycoside hydrolase families and exist as processive or nonprocessive enzymes. Product inhibition negatively impacts cellulase action, but experimental measurements of product-binding constants vary significantly, and there is little consensus on the importance of this phenomenon. To provide molecular level insights into cellulase product inhibition, we examine the impact of product binding on processive and nonprocessive cellulases by calculating the binding free energy of cellobiose to the product sites of catalytic domains of processive and nonprocessive enzymes from glycoside hydrolase families 6 and 7. The results suggest that cellobiose binds to processive cellulases much more strongly than nonprocessive cellulases. We also predict that the presence of a cellodextrin bound in the reactant site of the catalytic domain, which is present during enzymatic catalysis, has no effect on product binding in nonprocessive cellulases, whereas it significantly increases product binding to processive cellulases. This difference in product binding correlates with hydrogen bonding between the substrate-side ligand and the cellobiose product in processive cellulase tunnels and the additional stabilization from the longer tunnel-forming loops. The hydrogen bonds between the substrate- and product-side ligands are disrupted by water in nonprocessive cellulase clefts, and the lack of long tunnel-forming loops results in lower affinity of the product ligand. These findings provide new insights into the large discrepancies reported for binding constants for cellulases and suggest that product inhibition will vary significantly based on the amount of productive binding for processive cellulases on cellulose.
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Affiliation(s)
- Lintao Bu
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
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69
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Segato F, Damasio ARL, Gonçalves TA, Murakami MT, Squina FM, Polizeli M, Mort AJ, Prade RA. Two structurally discrete GH7-cellobiohydrolases compete for the same cellulosic substrate fiber. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:21. [PMID: 22494694 PMCID: PMC3431977 DOI: 10.1186/1754-6834-5-21] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 03/30/2012] [Indexed: 05/14/2023]
Abstract
BACKGROUND Cellulose consisting of arrays of linear beta-1,4 linked glucans, is the most abundant carbon-containing polymer present in biomass. Recalcitrance of crystalline cellulose towards enzymatic degradation is widely reported and is the result of intra- and inter-molecular hydrogen bonds within and among the linear glucans. Cellobiohydrolases are enzymes that attack crystalline cellulose. Here we report on two forms of glycosyl hydrolase family 7 cellobiohydrolases common to all Aspergillii that attack Avicel, cotton cellulose and other forms of crystalline cellulose. RESULTS Cellobiohydrolases Cbh1 and CelD have similar catalytic domains but only Cbh1 contains a carbohydrate-binding domain (CBD) that binds to cellulose. Structural superpositioning of Cbh1 and CelD on the Talaromyces emersonii Cel7A 3-dimensional structure, identifies the typical tunnel-like catalytic active site while Cbh1 shows an additional loop that partially obstructs the substrate-fitting channel. CelD does not have a CBD and shows a four amino acid residue deletion on the tunnel-obstructing loop providing a continuous opening in the absence of a CBD. Cbh1 and CelD are catalytically functional and while specific activity against Avicel is 7.7 and 0.5 U.mg prot-1, respectively specific activity on pNPC is virtually identical. Cbh1 is slightly more stable to thermal inactivation compared to CelD and is much less sensitive to glucose inhibition suggesting that an open tunnel configuration, or absence of a CBD, alters the way the catalytic domain interacts with the substrate. Cbh1 and CelD enzyme mixtures on crystalline cellulosic substrates show a strong combinatorial effort response for mixtures where Cbh1 is present in 2:1 or 4:1 molar excess. When CelD was overrepresented the combinatorial effort could only be partially overcome. CelD appears to bind and hydrolyze only loose cellulosic chains while Cbh1 is capable of opening new cellulosic substrate molecules away from the cellulosic fiber. CONCLUSION Cellobiohydrolases both with and without a CBD occur in most fungal genomes where both enzymes are secreted, and likely participate in cellulose degradation. The fact that only Cbh1 binds to the substrate and in combination with CelD exhibits strong synergy only when Cbh1 is present in excess, suggests that Cbh1 unties enough chains from cellulose fibers, thus enabling processive access of CelD.
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Affiliation(s)
- Fernando Segato
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | - André R L Damasio
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Department of Biochemistry, Ribeirão Preto School of Medicine, Ribeirão Preto, Sao Paulo, Brazil
| | - Thiago Augusto Gonçalves
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | - Mario T Murakami
- Laboratório Nacional de Biociências (LNBio), Campinas, Sao Paulo, Brazil
| | - Fabio M Squina
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | | | - Andrew J Mort
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, USA
| | - Rolf A Prade
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
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70
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Van Dyk JS, Pletschke BI. A review of lignocellulose bioconversion using enzymatic hydrolysis and synergistic cooperation between enzymes--factors affecting enzymes, conversion and synergy. Biotechnol Adv 2012; 30:1458-80. [PMID: 22445788 DOI: 10.1016/j.biotechadv.2012.03.002] [Citation(s) in RCA: 477] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/10/2012] [Accepted: 03/06/2012] [Indexed: 02/04/2023]
Abstract
Lignocellulose is a complex substrate which requires a variety of enzymes, acting in synergy, for its complete hydrolysis. These synergistic interactions between different enzymes have been investigated in order to design optimal combinations and ratios of enzymes for different lignocellulosic substrates that have been subjected to different pretreatments. This review examines the enzymes required to degrade various components of lignocellulose and the impact of pretreatments on the lignocellulose components and the enzymes required for degradation. Many factors affect the enzymes and the optimisation of the hydrolysis process, such as enzyme ratios, substrate loadings, enzyme loadings, inhibitors, adsorption and surfactants. Consideration is also given to the calculation of degrees of synergy and yield. A model is further proposed for the optimisation of enzyme combinations based on a selection of individual or commercial enzyme mixtures. The main area for further study is the effect of and interaction between different hemicellulases on complex substrates.
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Affiliation(s)
- J S Van Dyk
- Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa
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71
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Studies of Enzymatic Cleavage of Cellulose Using Polysaccharide Analysis by Carbohydrate gel Electrophoresis (PACE). Methods Enzymol 2012; 510:51-67. [DOI: 10.1016/b978-0-12-415931-0.00004-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
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72
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Abstract
Natural cellulolytic enzyme systems as well as leading commercial cellulase cocktails are dominated by enzymes that degrade cellulose chains in a processive manner. Despite the abundance of processivity among natural cellulases, the molecular basis as well as the biotechnological implications of this mechanism are only partly understood. One of the major limitations lies in the fact that it is not straightforward to measure and quantify processivity in what essentially are biphasic experimental systems. Here, we describe and discuss both well-established methods and newer methods for measuring cellulase processivity. In addition, we discuss recent insights from studies on chitinases that may help direct further studies on processivity in cellulases.
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Affiliation(s)
- Svein J Horn
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway
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73
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Marana SR. Structural and mechanistic fundamentals for designing of cellulases. Comput Struct Biotechnol J 2012; 2:e201209006. [PMID: 24688647 PMCID: PMC3962180 DOI: 10.5936/csbj.201209006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 09/20/2012] [Accepted: 09/23/2012] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sandro R Marana
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, São Paulo, 05513-970, SP, Brazil
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74
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Jeng WY, Wang NC, Lin CT, Shyur LF, Wang AHJ. Crystal structures of the laminarinase catalytic domain from Thermotoga maritima MSB8 in complex with inhibitors: essential residues for β-1,3- and β-1,4-glucan selection. J Biol Chem 2011; 286:45030-40. [PMID: 22065588 DOI: 10.1074/jbc.m111.271213] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Laminarinases hydrolyzing the β-1,3-linkage of glucans play essential roles in microbial saccharide degradation. Here we report the crystal structures at 1.65-1.82 Å resolution of the catalytic domain of laminarinase from the thermophile Thermotoga maritima with various space groups in the ligand-free form or in the presence of inhibitors gluconolactone and cetyltrimethylammonium. Ligands were bound at the cleft of the active site near an enclosure formed by Trp-232 and a flexible GASIG loop. A closed configuration at the active site cleft was observed in some molecules. The loop flexibility in the enzyme may contribute to the regulation of endo- or exo-activity of the enzyme and a preference to release laminaritrioses in long chain carbohydrate hydrolysis. Glu-137 and Glu-132 are proposed to serve as the proton donor and nucleophile, respectively, in the retaining catalysis of hydrolyzation. Calcium ions in the crystallization media are found to accelerate crystal growth. Comparison of laminarinase and endoglucanase structures revealed the subtle difference of key residues in the active site for the selection of β-1,3-glucan and β-1,4-glucan substrates, respectively. Arg-85 may be pivotal to β-1,3-glucan substrate selection. The similarity of the structures between the laminarinase catalytic domain and its carbohydrate-binding modules may have evolutionary relevance because of the similarities in their folds.
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Affiliation(s)
- Wen-Yih Jeng
- Institute of Biological Chemistry, Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei 115, Taiwan
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75
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Hu J, Arantes V, Saddler JN. The enhancement of enzymatic hydrolysis of lignocellulosic substrates by the addition of accessory enzymes such as xylanase: is it an additive or synergistic effect? BIOTECHNOLOGY FOR BIOFUELS 2011; 4:36. [PMID: 21974832 PMCID: PMC3198685 DOI: 10.1186/1754-6834-4-36] [Citation(s) in RCA: 222] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 10/05/2011] [Indexed: 05/05/2023]
Abstract
BACKGROUND We and other workers have shown that accessory enzymes, such as β-glucosidase, xylanase, and cellulase cofactors, such as GH61, can considerably enhance the hydrolysis effectiveness of cellulase cocktails when added to pretreated lignocellulosic substrates. It is generally acknowledged that, among the several factors that hamper our current ability to attain efficient lignocellulosic biomass conversion yields at low enzyme loadings, a major problem lies in our incomplete understanding of the cooperative action of the different enzymes acting on pretreated lignocellulosic substrates. RESULTS The reported work assessed the interaction between cellulase and xylanase enzymes and their potential to improve the hydrolysis efficiency of various pretreated lignocellulosic substrates when added at low protein loadings. When xylanases were added to the minimum amount of cellulase enzymes required to achieve 70% cellulose hydrolysis of steam pretreated corn stover (SPCS), or used to partially replace the equivalent cellulase dose, both approaches resulted in enhanced enzymatic hydrolysis. However, the xylanase supplementation approach increased the total protein loading required to achieve significant improvements in hydrolysis (an additive effect), whereas the partial replacement of cellulases with xylanase resulted in similar improvements in hydrolysis without increasing enzyme loading (a synergistic effect). The enhancement resulting from xylanase-aided synergism was higher when enzymes were added simultaneously at the beginning of hydrolysis. This co-hydrolysis of the xylan also influenced the gross fiber characteristics (for example, fiber swelling) resulting in increased accessibility of the cellulose to the cellulase enzymes. These apparent increases in accessibility enhanced the steam pretreated corn stover digestibility, resulting in three times faster cellulose and xylan hydrolysis, a seven-fold decrease in cellulase loading and a significant increase in the hydrolysis performance of the optimized enzyme mixture. When a similar xylanase-aided enhancement strategy was assessed on other pretreated lignocellulosic substrates, equivalent increases in hydrolysis efficiency were also observed. CONCLUSIONS It was apparent that the 'blocking effect' of xylan was one of the major mechanisms that limited the accessibility of the cellulase enzymes to the cellulose. However, the synergistic interaction of the xylanase and cellulase enzymes was also shown to significantly improve cellulose accessibility through increasing fiber swelling and fiber porosity and also plays a major role in enhancing enzyme accessibility.
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Affiliation(s)
- Jinguang Hu
- Forestry Products Biotechnology/Bioenergy Group, Wood Science Department, University of British Columbia, 2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
| | - Valdeir Arantes
- Forestry Products Biotechnology/Bioenergy Group, Wood Science Department, University of British Columbia, 2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
| | - Jack N Saddler
- Forestry Products Biotechnology/Bioenergy Group, Wood Science Department, University of British Columbia, 2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
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76
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Payne CM, Bomble YJ, Taylor CB, McCabe C, Himmel ME, Crowley MF, Beckham GT. Multiple functions of aromatic-carbohydrate interactions in a processive cellulase examined with molecular simulation. J Biol Chem 2011; 286:41028-35. [PMID: 21965672 DOI: 10.1074/jbc.m111.297713] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Proteins employ aromatic residues for carbohydrate binding in a wide range of biological functions. Glycoside hydrolases, which are ubiquitous in nature, typically exhibit tunnels, clefts, or pockets lined with aromatic residues for processing carbohydrates. Mutation of these aromatic residues often results in significant activity differences on insoluble and soluble substrates. However, the thermodynamic basis and molecular level role of these aromatic residues remain unknown. Here, we calculate the relative ligand binding free energy by mutating tryptophans in the Trichoderma reesei family 6 cellulase (Cel6A) to alanine. Removal of aromatic residues near the catalytic site has little impact on the ligand binding free energy, suggesting that aromatic residues immediately upstream of the active site are not directly involved in binding, but play a role in the glucopyranose ring distortion necessary for catalysis. Removal of aromatic residues at the entrance and exit of the Cel6A tunnel, however, dramatically impacts the binding affinity, suggesting that these residues play a role in chain acquisition and product stabilization, respectively. The roles suggested from differences in binding affinity are confirmed by molecular dynamics and normal mode analysis. Surprisingly, our results illustrate that aromatic-carbohydrate interactions vary dramatically depending on the position in the enzyme tunnel. As aromatic-carbohydrate interactions are present in all carbohydrate-active enzymes, these results have implications for understanding protein structure-function relationships in carbohydrate metabolism and recognition, carbon turnover in nature, and protein engineering strategies for biomass utilization. Generally, these results suggest that nature employs aromatic-carbohydrate interactions with a wide range of binding affinities for diverse functions.
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Affiliation(s)
- Christina M Payne
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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77
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Gao L, Wang F, Gao F, Wang L, Zhao J, Qu Y. Purification and characterization of a novel cellobiohydrolase (PdCel6A) from Penicillium decumbens JU-A10 for bioethanol production. BIORESOURCE TECHNOLOGY 2011; 102:8339-42. [PMID: 21723116 DOI: 10.1016/j.biortech.2011.06.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 05/02/2023]
Abstract
An acidic Cel6A, cellobiohydrolase (CBH) II, was purified from Penicillium decumbens and designated as PdCel6A. The deduced internal amino acid sequence of the novel CBH has a high degree of sequence identity with the CBH II from Aspergillus fumigatus. Surprisingly, PdCel6A exhibits characteristics comparable to that of CBH I, as well as CBH II. Similar to CBH I, the novel CBH has a specific activity of 1.9 IU/mg against p-nitrophenyl-β-d-cellobioside. The enzyme retains about 80% of its maximum activity after 4h of incubation at pH 2.0. Using delignified corncob residue as the substrate, ethanol concentration increased by 20% during simultaneous saccharification and fermentation when supplemented with low doses of PdCel6A (0.2mg/g substrate). To our knowledge, this is the first report involving a CBH I-like CBH II. The present paper provides new insight into the role of CBH II in cellulose degradation.
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Affiliation(s)
- Le Gao
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China
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78
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Phillips CM, Iavarone AT, Marletta MA. Quantitative Proteomic Approach for Cellulose Degradation by Neurospora crassa. J Proteome Res 2011; 10:4177-85. [DOI: 10.1021/pr200329b] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher M. Phillips
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Anthony T. Iavarone
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, California 94720, United States
| | - Michael A. Marletta
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, California 94720, United States
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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79
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Abstract
Cellulose is an abundant and renewable biopolymer that can be used for biofuel generation; however, structural entrapment with other cell wall components hinders enzyme-substrate interactions, a key bottleneck for ethanol production. Biomass is routinely subjected to treatments that facilitate cellulase-cellulose contacts. Cellulases and glucosidases act by hydrolyzing glycosidic bonds of linear glucose β-1,4-linked polymers, producing glucose. Here we describe eight high-temperature-operating cellulases (TCel enzymes) identified from a survey of thermobacterial and archaeal genomes. Three TCel enzymes preferentially hydrolyzed soluble cellulose, while two preferred insoluble cellulose such as cotton linters and filter paper. TCel enzymes had temperature optima ranging from 85°C to 102°C. TCel enzymes were stable, retaining 80% of initial activity after 120 h at 85°C. Two modes of cellulose breakdown, i.e., with endo- and exo-acting glucanases, were detected, and with two-enzyme combinations at 85°C, synergistic cellulase activity was observed for some enzyme combinations.
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80
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Takahashi M, Konishi T, Takeda T. Biochemical characterization of Magnaporthe oryzae β-glucosidases for efficient β-glucan hydrolysis. Appl Microbiol Biotechnol 2011; 91:1073-82. [DOI: 10.1007/s00253-011-3340-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 04/15/2011] [Accepted: 04/16/2011] [Indexed: 10/18/2022]
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81
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Liu YS, Baker JO, Zeng Y, Himmel ME, Haas T, Ding SY. Cellobiohydrolase hydrolyzes crystalline cellulose on hydrophobic faces. J Biol Chem 2011; 286:11195-201. [PMID: 21282110 PMCID: PMC3064174 DOI: 10.1074/jbc.m110.216556] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biodegradation of plant biomass is a slow process in nature, and hydrolysis of cellulose is also widely considered to be a rate-limiting step in the proposed industrial process of converting lignocellulosic materials to biofuels. It is generally known that a team of enzymes including endo- and exocellulases as well as cellobiases are required to act synergistically to hydrolyze cellulose to glucose. The detailed molecular mechanisms of these enzymes have yet to be convincingly elucidated. In this report, atomic force microscopy (AFM) is used to image in real-time the structural changes in Valonia cellulose crystals acted upon by the exocellulase cellobiohydrolase I (CBH I) from Trichoderma reesei. Under AFM, single enzyme molecules could be observed binding only to one face of the cellulose crystal, apparently the hydrophobic face. The surface roughness of cellulose began increasing after adding CBH I, and the overall size of cellulose crystals decreased during an 11-h period. Interestingly, this size reduction apparently occurred only in the width of the crystal, whereas the height remained relatively constant. In addition, the measured cross-section shape of cellulose crystal changed from asymmetric to nearly symmetric. These observed changes brought about by CBH I action may constitute the first direct visualization supporting the idea that the exocellulase selectively hydrolyzes the hydrophobic faces of cellulose. The limited accessibility of the hydrophobic faces in native cellulose may contribute significantly to the rate-limiting slowness of cellulose hydrolysis.
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Affiliation(s)
- Yu-San Liu
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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82
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Kurasin M, Väljamäe P. Processivity of cellobiohydrolases is limited by the substrate. J Biol Chem 2010; 286:169-77. [PMID: 21051539 DOI: 10.1074/jbc.m110.161059] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Processive cellobiohydrolases (CBHs) are the key components of fungal cellulase systems. Despite the wealth of structural data confirming the processive mode of action, little quantitative information on the processivity of CBHs is available. Here, we developed a method for measuring cellulase processivity. Sensitive fluorescence detection of enzyme-generated insoluble reducing groups on cellulose after labeling with diaminopyridine enabled quantification of the number of reducing-end exo-mode and endo-mode initiations. Both CBHs TrCel7A from Trichoderma reesei and PcCel7D from Phanerochaete chrysosporium employed reducing-end exo- and endo-mode initiation in parallel. Processivity values measured for TrCel7A and PcCel7D on cellulose hydrolysis were more than an order of magnitude lower than the values of intrinsic processivity that were found from the ratio of catalytic constant (k(cat)) and dissociation rate constant (k(off)). We propose that the length of the obstacle-free path available for a processive run on cellulose chain limits the processivity of CBHs on cellulose. TrCel7A and PcCel7D differed in their k(off) values, whereas the k(cat) values were similar. Furthermore, the k(off) values for endoglucanases (EGs) were much higher than the k(off) values for CBHs, whereas the k(cat) values for EGs and CBHs were within the same order of magnitude. These results suggest that the value of k(off) may be the primary target for the selection of cellulases.
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Affiliation(s)
- Mihhail Kurasin
- Institute of Molecular and Cell Biology, University of Tartu, Tartu 51014, Estonia
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83
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Lantz SE, Goedegebuur F, Hommes R, Kaper T, Kelemen BR, Mitchinson C, Wallace L, Ståhlberg J, Larenas EA. Hypocrea jecorina CEL6A protein engineering. BIOTECHNOLOGY FOR BIOFUELS 2010; 3:20. [PMID: 20822549 PMCID: PMC2945327 DOI: 10.1186/1754-6834-3-20] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 09/08/2010] [Indexed: 05/03/2023]
Abstract
The complex technology of converting lignocellulose to fuels such as ethanol has advanced rapidly over the past few years, and enzymes are a critical component of this technology. The production of effective enzyme systems at cost structures that facilitate commercial processes has been the focus of research for many years. Towards this end, the H. jecorina cellobiohydrolases, CEL7A and CEL6A, have been the subject of protein engineering at Genencor. Our first rounds of cellobiohydrolase engineering were directed towards improving the thermostability of both of these enzymes and produced variants of CEL7A and CEL6A with apparent melting temperatures above 70°C, placing their stability on par with that of H. jecorina CEL5A (EG2) and CEL3A (BGL1). We have now moved towards improving CEL6A- and CEL7A-specific performance in the context of a complete enzyme system under industrially relevant conditions. Achievement of these goals required development of new screening strategies and tools. We discuss these advances along with some results, focusing mainly on engineering of CEL6A.
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Affiliation(s)
- Suzanne E Lantz
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Frits Goedegebuur
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Ronald Hommes
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Thijs Kaper
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Bradley R Kelemen
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Colin Mitchinson
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Louise Wallace
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Jerry Ståhlberg
- Department of Molecular Biology, Swedish University of Agricultural Sciences, POB 590, SE-751 24 Uppsala, Sweden
| | - Edmundo A Larenas
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
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84
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Liu G, Wei X, Qin Y, Qu Y. Characterization of the endoglucanase and glucomannanase activities of a glycoside hydrolase family 45 protein from Penicillium decumbens 114-2. J GEN APPL MICROBIOL 2010; 56:223-9. [PMID: 20647679 DOI: 10.2323/jgam.56.223] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The gene encoding a glycoside hydrolase (GH) family 45 endoglucanase (Cel45A) was cloned from P. decumbens 114-2 and expressed in Pichia pastoris. To our knowledge, this is the first report of characterization of a GH family 45 protein from Penicillium species. The purified recombinant enzyme showed a higher activity on konjac glucomannan (KGM) than on sodium carboxymethyl cellulose (CMC-Na) or phosphoric acid swollen cellulose (PASC). The highest hydrolytic activity was detected at pH5.0 on KGM and pH 3.5 on CMC-Na, indicating the mode of action on the two substrates may be different for Cel45A. The optimum temperatures on the two substrates were both 60 degrees C and about 90% relative activities were retained at 70 degrees C. Products released from PASC and CMC-Na were mainly cellobiose, cellotriose and cellotetraose. The protein with higher glucomannanase activity might help the efficient degradation of lignocellulose by P. decumbens in the natural state.
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Affiliation(s)
- Guodong Liu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, Shandong, P.R. China
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85
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Characterization of a cellobiohydrolase (MoCel6A) produced by Magnaporthe oryzae. Appl Environ Microbiol 2010; 76:6583-90. [PMID: 20709852 DOI: 10.1128/aem.00618-10] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Three GH-6 family cellobiohydrolases are expected in the genome of Magnaporthe grisea based on the complete genome sequence. Here, we demonstrate the properties, kinetics, and substrate specificities of a Magnaporthe oryzae GH-6 family cellobiohydrolase (MoCel6A). In addition, the effect of cellobiose on MoCel6A activity was also investigated. MoCel6A contiguously fused to a histidine tag was overexpressed in M. oryzae and purified by affinity chromatography. MoCel6A showed higher hydrolytic activities on phosphoric acid-swollen cellulose (PSC), β-glucan, and cellooligosaccharide derivatives than on cellulose, of which the best substrates were cellooligosaccharides. A tandemly aligned cellulose binding domain (CBD) at the N terminus caused increased activity on cellulose and PSC, whereas deletion of the CBD (catalytic domain only) showed decreased activity on cellulose. MoCel6A hydrolysis of cellooligosaccharides and sulforhodamine-conjugated cellooligosaccharides was not inhibited by exogenously adding cellobiose up to 438 mM, which, rather, enhanced activity, whereas a GH-7 family cellobiohydrolase from M. oryzae (MoCel7A) was severely inhibited by more than 29 mM cellobiose. Furthermore, we assessed the effects of cellobiose on hydrolytic activities using MoCel6A and Trichoderma reesei cellobiohydrolase (TrCel6A), which were prepared in Aspergillus oryzae. MoCel6A showed increased hydrolysis of cellopentaose used as a substrate in the presence of 292 mM cellobiose at pH 4.5 and pH 6.0, and enhanced activity disappeared at pH 9.0. In contrast, TrCel6A exhibited slightly increased hydrolysis at pH 4.5, and hydrolysis was severely inhibited at pH 9.0. These results suggest that enhancement or inhibition of hydrolytic activities by cellobiose is dependent on the reaction mixture pH.
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86
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Wang L, Wang Y, Ragauskas AJ. A novel FRET approach for in situ investigation of cellulase–cellulose interaction. Anal Bioanal Chem 2010; 398:1257-62. [DOI: 10.1007/s00216-010-4057-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2010] [Revised: 07/09/2010] [Accepted: 07/21/2010] [Indexed: 10/19/2022]
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87
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Jeng WY, Wang NC, Lin MH, Lin CT, Liaw YC, Chang WJ, Liu CI, Liang PH, Wang AHJ. Structural and functional analysis of three β-glucosidases from bacterium Clostridium cellulovorans, fungus Trichoderma reesei and termite Neotermes koshunensis. J Struct Biol 2010; 173:46-56. [PMID: 20682343 DOI: 10.1016/j.jsb.2010.07.008] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 07/17/2010] [Accepted: 07/29/2010] [Indexed: 11/18/2022]
Abstract
β-glucosidases (EC 3.2.1.21) cleave β-glucosidic linkages in disaccharide or glucose-substituted molecules and play important roles in fundamental biological processes. β-Glucosidases have been widely used in agricultural, biotechnological, industrial and medical applications. In this study, a high yield expression (70-250 mg/l) in Escherichia coli of the three functional β-glucosidase genes was obtained from the bacterium Clostridium cellulovorans (CcBglA), the fungus Trichoderma reesei (TrBgl2), and the termite Neotermes koshunensis (NkBgl) with the crystal structures of CcBglA, TrBgl2 and NkBgl, determined at 1.9Å, 1.63Å and 1.34Å resolution, respectively. The overall structures of these enzymes are similar to those belonging to the β-retaining glycosyl hydrolase family 1, which have a classical (α/β)(8)-TIM barrel fold. Each contains a slot-like active site cleft and a more variable outer opening, related to its function in processing different lengths of β-1,4-linked glucose derivatives. The two essential glutamate residues for hydrolysis are spatially conserved in the active site. In both TrBgl2 and NkBgl structures, a Tris molecule was found to bind at the active site, explaining the slight inhibition of hydrolase activity observed in Tris buffer. Manganese ions at 10mM exerted an approximate 2-fold enzyme activity enhancement of all three β-glucosidases, with CcBglA catalyzing the most efficiently in hydrolysis reaction and tolerating Tris as well as some metal inhibition. In summary, our results for the structural and functional properties of these three β-glucosidases from various biological sources open important avenues of exploration for further practical applications.
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Affiliation(s)
- Wen-Yih Jeng
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
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88
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Michaelsen A, Piñar G, Pinzari F. Molecular and microscopical investigation of the microflora inhabiting a deteriorated Italian manuscript dated from the thirteenth century. MICROBIAL ECOLOGY 2010; 60:69-80. [PMID: 20449583 PMCID: PMC2917558 DOI: 10.1007/s00248-010-9667-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 03/12/2010] [Indexed: 05/07/2023]
Abstract
This case study shows the application of nontraditional diagnostic methods to investigate the microbial consortia inhabiting an ancient manuscript. The manuscript was suspected to be biologically deteriorated and SEM observations showed the presence of fungal spores attached to fibers, but classic culturing methods did not succeed in isolating microbial contaminants. Therefore, molecular methods, including PCR, denaturing gradient gel electrophoresis (DGGE), and clone libraries, were used as a sensitive alternative to conventional cultivation techniques. DGGE fingerprints revealed a high biodiversity of both bacteria and fungi inhabiting the manuscript. DNA sequence analysis confirmed the existence of fungi and bacteria in manuscript samples. A number of fungal clones identified on the manuscript showed similarity to fungal species inhabiting dry or saline environments, suggesting that the manuscript environment selects for osmophilic or xerophilic fungal species. Most of the bacterial sequences retrieved from the manuscript belong to phylotypes with cellulolytic activities.
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Affiliation(s)
- Astrid Michaelsen
- Department of Microbial Ecology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Guadalupe Piñar
- Institute of Applied Microbiology, Department of Biotechnology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Flavia Pinzari
- Laboratorio di Biologia, Ministero per i Beni e le Attività Culturali, ICPAL - Istituto Centrale per il Restauro e la Conservazione del Patrimonio Archivistico e Librario, Via Milano, 76, 00184 Rome, Italy
- Dept. of Plant Biology, School in Ecological Sciences, Sapienza University of Rome, Rome, Italy
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89
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Santa-Maria M, Jeoh T. Molecular-Scale Investigations of Cellulose Microstructure during Enzymatic Hydrolysis. Biomacromolecules 2010; 11:2000-7. [DOI: 10.1021/bm100366h] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Monica Santa-Maria
- Biological and Agricultural Engineering, University of California, One Shields Avenue, Davis, California 95616
| | - Tina Jeoh
- Biological and Agricultural Engineering, University of California, One Shields Avenue, Davis, California 95616
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90
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Moraïs S, Heyman A, Barak Y, Caspi J, Wilson DB, Lamed R, Shoseyov O, Bayer EA. Enhanced cellulose degradation by nano-complexed enzymes: Synergism between a scaffold-linked exoglucanase and a free endoglucanase. J Biotechnol 2010; 147:205-11. [PMID: 20438772 DOI: 10.1016/j.jbiotec.2010.04.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 04/13/2010] [Accepted: 04/23/2010] [Indexed: 11/19/2022]
Abstract
Protein molecular scaffolds are attracting interest as natural candidates for the presentation of enzymes and acceleration of catalytic reactions. We have previously reported evidence that the stable protein 1 (SP1) from Populustremula can be employed as a molecular scaffold for the presentation of either catalytic or structural binding (cellulosomal cohesin) modules. In the present work, we have displayed a potent exoglucanase (Cel6B) from the aerobic cellulolytic bacterium, Thermobifida fusca, on a cohesin-bearing SP1 scaffold. For this purpose, a chimaeric form of the enzyme, fused to a cellulosomal dockerin module, was prepared. Full incorporation of 12 dockerin-bearing exoglucanase molecules onto the cohesin-bearing scaffold was achieved. Cellulase activity was tested on two cellulosic substrates with different levels of crystallinity, and the activity of the scaffold-linked exoglucanase was significantly reduced, compared to the free dockerin-containing enzyme. However, addition of relatively low concentrations of a free wild-type endoglucanase (T. fusca Cel5A) that bears a cellulose-binding module, in combination with the complexed exoglucanase resulted in a marked rise in activity on both cellulosic substrates. The endoglucanase cleaves internal sites of the cellulose chains, and the new chain ends of the substrate were now readily accessible to the scaffold-borne exoglucanase, thereby resulting in highly effective, synergistic degradation of cellulosic substrates.
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Affiliation(s)
- Sarah Moraïs
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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91
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Contribution of a xylan-binding module to the degradation of a complex cellulosic substrate by designer cellulosomes. Appl Environ Microbiol 2010; 76:3787-96. [PMID: 20400556 DOI: 10.1128/aem.00266-10] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Conversion of components of the Thermobifida fusca free-enzyme system to the cellulosomal mode using the designer cellulosome approach can be employed to discover the properties and inherent advantages of the cellulosome system. In this article, we describe the conversion of the T. fusca xylanases Xyn11A and Xyn10B and their synergistic interaction in the free state or within designer cellulosome complexes in order to enhance specific degradation of hatched wheat straw as a model for a complex cellulosic substrate. Endoglucanase Cel5A from the same bacterium and its recombinant dockerin-containing chimera were also studied for their combined effect, together with the xylanases, on straw degradation. Synergism was demonstrated when Xyn11A was combined with Xyn10B and/or Cel5A, and approximately 1.5-fold activity enhancements were achieved by the designer cellulosome complexes compared to the free wild-type enzymes. These improvements in activity were due to both substrate-targeting and proximity effects among the enzymes contained in the designer cellulosome complexes. The intrinsic cellulose/xylan-binding module (XBM) of Xyn11A appeared to be essential for efficient substrate degradation. Indeed, only designer cellulosomes in which the XBM was maintained as a component of Xyn11A achieved marked enhancement in activity compared to the combination of wild-type enzymes. Moreover, integration of the XBM in designer cellulosomes via a dockerin module (separate from the Xyn11A catalytic module) failed to enhance activity, suggesting a role in orienting the parent xylanase toward its preferred polysaccharide component of the complex wheat straw substrate. The results provide novel mechanistic insight into the synergistic activity of designer cellulosome components on natural plant cell wall substrates.
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92
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Quirk A, Lipkowski J, Vandenende C, Cockburn D, Clarke AJ, Dutcher JR, Roscoe SG. Direct visualization of the enzymatic digestion of a single fiber of native cellulose in an aqueous environment by atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:5007-13. [PMID: 20170174 DOI: 10.1021/la9037028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Atomic force microscopy (AFM) was used to study native cellulose films prepared from a bacterial cellulose source, Acetobacter xylinum, using a novel application of the Langmuir-Blodgett technique. These films allowed high-resolution AFM images of single fibers and their microfibril structure to be obtained. Two types of experiments were performed. First, the fibers were characterized using samples that were dried after LB deposition. Next, novel protocols that allowed us to image single fibers of cellulose in films that were never dried were developed. This procedure allowed us to perform in situ AFM imaging studies of the enzymatic hydrolysis of single cellulose fibers in solution using cellulolytic enzymes. The in situ degradation of cellulose fibers was monitored over a 9 h period using AFM. These studies provided the first direct, real-time images of the enzymatic degradation of a single cellulose fiber. We have demonstrated the tremendous potential of AFM to study the mechanism of the enzymatic digestion of cellulose and to identify the most effective enzymes for the digestion of various cellulose structures or isomorphs.
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Affiliation(s)
- Amanda Quirk
- Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1 Canada
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93
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Yeoman CJ, Han Y, Dodd D, Schroeder CM, Mackie RI, Cann IKO. Thermostable enzymes as biocatalysts in the biofuel industry. ADVANCES IN APPLIED MICROBIOLOGY 2010; 70:1-55. [PMID: 20359453 DOI: 10.1016/s0065-2164(10)70001-0] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Lignocellulose is the most abundant carbohydrate source in nature and represents an ideal renewable energy source. Thermostable enzymes that hydrolyze lignocellulose to its component sugars have significant advantages for improving the conversion rate of biomass over their mesophilic counterparts. We review here the recent literature on the development and use of thermostable enzymes for the depolymerization of lignocellulosic feedstocks for biofuel production. Furthermore, we discuss the protein structure, mechanisms of thermostability, and specific strategies that can be used to improve the thermal stability of lignocellulosic biocatalysts.
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Affiliation(s)
- Carl J Yeoman
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
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94
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95
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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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96
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Xu F, Ding H, Tejirian A. Detrimental effect of cellulose oxidation on cellulose hydrolysis by cellulase. Enzyme Microb Technol 2009. [DOI: 10.1016/j.enzmictec.2009.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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97
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Effects of Supplementing a Fibrolytic Feed Enzyme on the Growth Performance and Carcass Characteristics of Beef Steers1. ACTA ACUST UNITED AC 2009. [DOI: 10.15232/s1080-7446(15)30729-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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98
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Suginta W, Pantoom S, Prinz H. Substrate binding modes and anomer selectivity of chitinase A from Vibrio harveyi. J Chem Biol 2009; 2:191-202. [PMID: 19568782 PMCID: PMC2763143 DOI: 10.1007/s12154-009-0021-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Accepted: 05/07/2009] [Indexed: 11/30/2022] Open
Abstract
High-performance liquid chromatography mass spectrometry (HPLC MS) was employed to assess the binding behaviors of various substrates to Vibrio harveyi chitinase A. Quantitative analysis revealed that hexaNAG preferred subsites −2 to +2 over subsites −3 to +2 and pentaNAG only required subsites −2 to +2, while subsites −4 to +2 were not used at all by both substrates. The results suggested that binding of the chitooligosaccharides to the enzyme essentially occurred in compulsory fashion. The symmetrical binding mode (−2 to +2) was favored presumably to allow the natural form of sugars to be utilized effectively. Crystalline α chitin was initially hydrolyzed into a diverse ensemble of chitin oligomers, providing a clear sign of random attacks that took place within chitin chains. However, the progressive degradation was shown to occur in greater extent at later time to complete hydrolysis. The effect of the reducing-end residues were also investigated by means of HPLC MS. Substitutions of Trp275 to Gly and Trp397 to Phe significantly shifted the anomer selectivity of the enzyme toward β substrates. The Trp275 mutation modulated the kinetic property of the enzyme by decreasing the catalytic constant (kcat) and the substrate specificity (kcat/Km) toward all substrates by five- to tenfold. In contrast, the Trp397 mutation weakened the binding strength at subsite (+2), thereby speeding up the rate of the enzymatic cleavage toward soluble substrates but slowing down the rate of the progressive degradation toward insoluble chitin.
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Affiliation(s)
- Wipa Suginta
- Biochemistry-Electrochemistry Research Unit, School of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon, Ratchasima, 30000, Thailand,
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99
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Physical state of κ-carrageenan modulates the mode of action of κ-carrageenase from Pseudoalteromonas carrageenovora. Biochem J 2009; 419:545-53. [DOI: 10.1042/bj20080619] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Pseudoalteromonas carrageenovora κ-carrageenase is a glycoside hydrolase involved in the bioconversion of carrageenans. Carrageenans are sulfated galactans that are densely packed in red algal cell walls. Previous crystallographic investigations revealed that the active site of κ-carrageenase has a tunnel-shaped topology, suggesting a processive mode of action for this enzyme. To biochemically characterize the enzymatic depolymerization of κ-carrageenan, soluble and solid substrates (in both gel and powder forms) were incubated with P. carrageenovora κ-carrageenase. The average molecular mass of soluble carrageenan decreased rapidly, and all possible degradation products were observed, suggesting random degradation of κ-carrageenan. In contrast, as expected for a processive-type carrageenase, the average molecular mass of solid carrageenan decreased very slowly, and tetrasaccharide production was high. Interestingly, experimentally determined processivity was similar for gel and powder, suggesting that, in addition to an adapted catalytic site, the substrate must be in the solid state for κ-carrageenase processivity to operate, whatever the level of carrageenan ordering.
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100
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Zhou J, Wang YH, Chu J, Luo LZ, Zhuang YP, Zhang SL. Optimization of cellulase mixture for efficient hydrolysis of steam-exploded corn stover by statistically designed experiments. BIORESOURCE TECHNOLOGY 2009; 100:819-25. [PMID: 18771915 DOI: 10.1016/j.biortech.2008.06.068] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 06/24/2008] [Accepted: 06/24/2008] [Indexed: 05/10/2023]
Abstract
To improve the enzymatic hydrolytic efficiency and reduce production cost, a statistically designed experimental approach was used to optimize the composition of cellulase mixture so as to maximize the amount of glucose produced from steam-exploded corn stover (SECS). Using seven purified enzymes (cellobiohydrolases, Cel7A, Cel6A, Cel6B; endoglucanases, Cel7B, Cel12A, Cel61A; and beta-glucosidase) from Trichoderma viride T 100-14 mutant strain, a multi-enzyme mixture was constituted after screening and optimization. The final optimal composition (mol%) of the multi-enzyme mixture was Cel7A (19.8%), Cel6A (37.5%), Cel6B (4.7%), Cel7B (17.7%), Cel12A (15.2%), Cel61A (2.3%) and beta-glucosidase (2.8%). The subsequent verification experiments followed by glucose assay together with scanning electron microscopy (SEM) observation confirmed the validity of the models. The multi-enzyme mixture displayed a high performance in converting the cellulosic substrate (SECS). The amount of glucose produced (15.5mg/ml) was 2.1 times as that of the crude cellulase preparation. The results indicated that the optimized cellulase mixture is an available and efficient paradigm for the hydrolysis of lignocellulosic substrate. The enhanced cellulolytic activity displayed by the constructed cellulase mixture could be used as an effective tool for producing bioethanol efficiently from cellulose.
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Affiliation(s)
- Jin Zhou
- State Key Laboratory of Bioreactor Engineering, National Engineering Research Center for Biotechnology (Shanghai), East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
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