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A Predicted Mannoprotein Participates in Cryptococcus gattii Capsular Structure. mSphere 2018; 3:3/2/e00023-18. [PMID: 29897877 PMCID: PMC5917426 DOI: 10.1128/msphere.00023-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 04/02/2018] [Indexed: 11/20/2022] Open
Abstract
The yeast-like pathogen Cryptococcus gattii is an etiological agent of cryptococcosis. The major cryptococcal virulence factor is the polysaccharide capsule, which is composed of glucuronoxylomannan (GXM), galactoxylomannan (GalXM), and mannoproteins (MPs). The GXM and GalXM polysaccharides have been extensively characterized; however, there is little information about the role of mannoproteins in capsule assembly and their participation in yeast pathogenicity. The present study characterized the function of a predicted mannoprotein from C. gattii, designated Krp1. Loss-of-function and gain-of-function mutants were generated, and phenotypes associated with the capsular architecture were evaluated. The null mutant cells were more sensitive to a cell wall stressor that disrupts beta-glucan synthesis. Also, these cells displayed increased GXM release to the culture supernatant than the wild-type strain did. The loss of Krp1 influenced cell-associated cryptococcal polysaccharide thickness and phagocytosis by J774.A1 macrophages in the early hours of interaction, but no difference in virulence in a murine model of cryptococcosis was observed. In addition, recombinant Krp1 was antigenic and differentially recognized by serum from an individual with cryptococcosis, but not with serum from an individual with candidiasis. Taken together, these results indicate that C. gattii Krp1 is important for the cell wall structure, thereby influencing capsule assembly, but is not essential for virulence in vivoIMPORTANCECryptococcus gattii has the ability to escape from the host's immune system through poorly understood mechanisms and can lead to the death of healthy individuals. The role of mannoproteins in C. gattii pathogenicity is not completely understood. The present work characterized a protein, Kpr1, that is essential for the maintenance of C. gattii main virulence factor, the polysaccharide capsule. Our data contribute to the understanding of the role of Kpr1 in capsule structuring, mainly by modulating the distribution of glucans in C. gattii cell wall.
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Lecarme L, Kochem A, Chiang L, Moutet J, Berthiol F, Philouze C, Leconte N, Storr T, Thomas F. Electronic Structure and Reactivity of One-Electron-Oxidized Copper(II) Bis(phenolate)–Dipyrrin Complexes. Inorg Chem 2018; 57:9708-9719. [DOI: 10.1021/acs.inorgchem.8b00044] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Lauréline Lecarme
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Amélie Kochem
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Linus Chiang
- Department of Chemistry, University of the Fraser Valley, Abbotsford, British Columbia V2S 7M8, Canada
| | - Jules Moutet
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Florian Berthiol
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Christian Philouze
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Nicolas Leconte
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Tim Storr
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Fabrice Thomas
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
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Reisky L, Büchsenschütz HC, Engel J, Song T, Schweder T, Hehemann JH, Bornscheuer UT. Oxidative demethylation of algal carbohydrates by cytochrome P450 monooxygenases. Nat Chem Biol 2018; 14:342-344. [PMID: 29459682 DOI: 10.1038/s41589-018-0005-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 12/20/2017] [Indexed: 01/22/2023]
Abstract
Sugar O-methylation shields algal polysaccharides against microbial hydrolytic enzymes. Here, we describe cytochrome P450 monooxygenases from marine bacteria that, together with appropriate redox-partner proteins, catalyze the oxidative demethylation of 6-O-methyl-D-galactose, which is an abundant monosaccharide of the algal polysaccharides agarose and porphyran. This previously unknown biological function extends the group of carbohydrate-active enzymes to include the class of cytochrome P450 monooxygenases.
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Affiliation(s)
- Lukas Reisky
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Hanna C Büchsenschütz
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Jennifer Engel
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Tao Song
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Thomas Schweder
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Jan-Hendrik Hehemann
- Max Planck Institute for Marine Microbiology, Bremen, Germany. .,University of Bremen, Center for Marine Environmental Sciences (MARUM), Bremen, Germany.
| | - Uwe T Bornscheuer
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, Greifswald, Germany.
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54
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Substrate-based differential expression analysis reveals control of biomass degrading enzymes in Pycnoporus cinnabarinus. Biochem Eng J 2018. [DOI: 10.1016/j.bej.2017.11.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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55
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Liu J, Wu S, Li Z. Recent advances in enzymatic oxidation of alcohols. Curr Opin Chem Biol 2017; 43:77-86. [PMID: 29258054 DOI: 10.1016/j.cbpa.2017.12.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/03/2017] [Accepted: 12/04/2017] [Indexed: 01/07/2023]
Abstract
Enzymatic alcohol oxidation plays an important role in chemical synthesis. In the past two years, new alcohol oxidation enzymes were developed through genome-mining and protein engineering, such as new copper radical oxidases with broad substrate scope, alcohol dehydrogenases with altered cofactor preference and a flavin-dependent alcohol oxidase with enhanced oxygen coupling. New cofactor recycling methods were reported for alcohol dehydrogenase-catalyzed oxidation with photocatalyst and coupled glutaredoxin-glutathione reductase as promising examples. Different alcohol oxidation systems were used for the oxidation of primary and secondary alcohols, especially in the cascade conversion of alcohols to lactones, lactams, chiral amines, chiral alcohols and hydroxyketones. Among them, biocatalyst with low enantioselectivity demonstrated an interesting feature for complete conversion of racemic secondary alcohols through non-enantioselective oxidation.
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Affiliation(s)
- Ji Liu
- Department of Chemical and Biomolecular Engineering, 4 Engineering Drive 4, National University of Singapore, Singapore 117585, Singapore
| | - Shuke Wu
- Department of Chemical and Biomolecular Engineering, 4 Engineering Drive 4, National University of Singapore, Singapore 117585, Singapore
| | - Zhi Li
- Department of Chemical and Biomolecular Engineering, 4 Engineering Drive 4, National University of Singapore, Singapore 117585, Singapore.
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Janusz G, Pawlik A, Sulej J, Swiderska-Burek U, Jarosz-Wilkolazka A, Paszczynski A. Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution. FEMS Microbiol Rev 2017; 41:941-962. [PMID: 29088355 PMCID: PMC5812493 DOI: 10.1093/femsre/fux049] [Citation(s) in RCA: 354] [Impact Index Per Article: 50.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 10/12/2017] [Indexed: 12/11/2022] Open
Abstract
Extensive research efforts have been dedicated to describing degradation of wood, which is a complex process; hence, microorganisms have evolved different enzymatic and non-enzymatic strategies to utilize this plentiful plant material. This review describes a number of fungal and bacterial organisms which have developed both competitive and mutualistic strategies for the decomposition of wood and to thrive in different ecological niches. Through the analysis of the enzymatic machinery engaged in wood degradation, it was possible to elucidate different strategies of wood decomposition which often depend on ecological niches inhabited by given organism. Moreover, a detailed description of low molecular weight compounds is presented, which gives these organisms not only an advantage in wood degradation processes, but seems rather to be a new evolutionatory alternative to enzymatic combustion. Through analysis of genomics and secretomic data, it was possible to underline the probable importance of certain wood-degrading enzymes produced by different fungal organisms, potentially giving them advantage in their ecological niches. The paper highlights different fungal strategies of wood degradation, which possibly correlates to the number of genes coding for secretory enzymes. Furthermore, investigation of the evolution of wood-degrading organisms has been described.
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Affiliation(s)
- Grzegorz Janusz
- Department of Biochemistry, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, Poland
| | - Anna Pawlik
- Department of Biochemistry, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, Poland
| | - Justyna Sulej
- Department of Biochemistry, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, Poland
| | - Urszula Swiderska-Burek
- Department of Botany and Mycology, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, Poland
| | - Anna Jarosz-Wilkolazka
- Department of Biochemistry, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, Poland
| | - Andrzej Paszczynski
- School of Food Science, Food Research Center, Room 103, University of Idaho, Moscow, ID 83844, USA
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A Novel Colletotrichum graminicola Raffinose Oxidase in the AA5 Family. Appl Environ Microbiol 2017; 83:AEM.01383-17. [PMID: 28778886 DOI: 10.1128/aem.01383-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 07/24/2017] [Indexed: 12/17/2022] Open
Abstract
We describe here the identification and characterization of a copper radical oxidase from auxiliary activities family 5 (AA5_2) that was distinguished by showing preferential activity toward raffinose. Despite the biotechnological potential of carbohydrate oxidases from family AA5, very few members have been characterized. The gene encoding raffinose oxidase from Colletotrichum graminicola (CgRaOx; EC 1.1.3.-) was identified utilizing a bioinformatics approach based on the known modular structure of a characterized AA5_2 galactose oxidase. CgRaOx was expressed in Pichia pastoris, and the purified enzyme displayed the highest activity on the trisaccharide raffinose, whereas the activity on the disaccharide melibiose was three times lower and more than ten times lower activity was detected on d-galactose at a 300 mM substrate concentration. Thus, the substrate preference of CgRaOx was distinguished clearly from the substrate preferences of the known galactose oxidases. The site of oxidation for raffinose was studied by 1H nuclear magnetic resonance and mass spectrometry, and we confirmed that the hydroxyl group at the C-6 position was oxidized to an aldehyde and that in addition uronic acid was produced as a side product. A new electrospray ionization mass spectrometry method for the identification of C-6 oxidized products was developed, and the formation mechanism of the uronic acid was studied. CgRaOx presented a novel activity pattern in the AA5 family.IMPORTANCE Currently, there are only a few characterized members of the CAZy AA5 protein family. These enzymes are interesting from an application point of view because of their ability to utilize the cheap and abundant oxidant O2 without the requirement of complex cofactors such as FAD or NAD(P). Here, we present the identification and characterization of a novel AA5 member from Colletotrichum graminicola As discussed in the present study, the bioinformatics approach using the modular structure of galactose oxidase was successful in finding a C-6 hydroxyl carbohydrate oxidase having substrate preference for the trisaccharide raffinose. By the discovery of this activity, the diversity of the CAZy AA5 family is increasing.
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58
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Glyoxal oxidases: their nature and properties. World J Microbiol Biotechnol 2017; 33:87. [DOI: 10.1007/s11274-017-2254-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 03/29/2017] [Indexed: 01/30/2023]
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59
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L-Threonine and its analogue added to autoclaved solid medium suppress trichothecene production by Fusarium graminearum. Arch Microbiol 2017; 199:945-952. [PMID: 28357472 DOI: 10.1007/s00203-017-1364-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 09/18/2016] [Accepted: 03/15/2017] [Indexed: 12/30/2022]
Abstract
Fusarium graminearum produces trichothecene mycotoxins under certain nutritional conditions. When L-Thr and its analogue L-allo-threonine were added to brown rice flour solid medium before inoculation, trichothecene production after 4 days of incubation was suppressed. A time-course analysis of gene expression demonstrated that L-Thr suppressed transcription of Tri6, a trichothecene master regulator gene, and a terpene cyclase Tri5 gene. Regulation of trichothecene biosynthesis by altering major primary metabolic processes may open up the possibility to develop safe chemicals for the reduction of mycotoxin contamination might be developed.
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60
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Dalecki AG, Crawford CL, Wolschendorf F. Copper and Antibiotics: Discovery, Modes of Action, and Opportunities for Medicinal Applications. Adv Microb Physiol 2017; 70:193-260. [PMID: 28528648 DOI: 10.1016/bs.ampbs.2017.01.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Copper is a ubiquitous element in the environment as well as living organisms, with its redox capabilities and complexation potential making it indispensable for many cellular functions. However, these same properties can be highly detrimental to prokaryotes and eukaryotes when not properly controlled, damaging many biomolecules including DNA, lipids, and proteins. To restrict free copper concentrations, all bacteria have developed mechanisms of resistance, sequestering and effluxing labile copper to minimize its deleterious effects. This weakness is actively exploited by phagocytes, which utilize a copper burst to destroy pathogens. Though administration of free copper is an unreasonable therapeutic antimicrobial itself, due to insufficient selectivity between host and pathogen, small-molecule ligands may provide an opportunity for therapeutic mimicry of the immune system. By modulating cellular entry, complex stability, resistance evasion, and target selectivity, ligand/metal coordination complexes can synergistically result in high levels of antibacterial activity. Several established therapeutic drugs, such as disulfiram and pyrithione, display remarkable copper-dependent inhibitory activity. These findings have led to development of new drug discovery techniques, using copper ions as the focal point. High-throughput screens for copper-dependent inhibitors against Mycobacterium tuberculosis and Staphylococcus aureus uncovered several new compounds, including a new class of inhibitors, the NNSNs. In this review, we highlight the microbial biology of copper, its antibacterial activities, and mechanisms to discover new inhibitors that synergize with copper.
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Affiliation(s)
- Alex G Dalecki
- The University of Alabama at Birmingham, Birmingham, AL, United States
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61
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Active-site maturation and activity of the copper-radical oxidase GlxA are governed by a tryptophan residue. Biochem J 2017; 474:809-825. [DOI: 10.1042/bcj20160968] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/02/2017] [Accepted: 01/13/2017] [Indexed: 11/17/2022]
Abstract
GlxA from Streptomyces lividans is a mononuclear copper-radical oxidase and a member of the auxiliary activity family 5 (AA5). Its domain organisation and low sequence homology make it a distinct member of the AA5 family in which the fungal galactose 6-oxidase (Gox) is the best characterised. GlxA is a key cuproenzyme in the copper-dependent morphological development of S. lividans with a function that is linked to the processing of an extracytoplasmic glycan. The catalytic sites in GlxA and Gox contain two distinct one-electron acceptors comprising the copper ion and a 3′-(S-cysteinyl) tyrosine. The latter is formed post-translationally through a covalent bond between a cysteine and a copper-co-ordinating tyrosine ligand and houses a radical. In GlxA and Gox, a second co-ordination sphere tryptophan residue (Trp288 in GlxA) is present, but the orientation of the indole ring differs between the two enzymes, creating a marked difference in the π–π stacking interaction of the benzyl ring with the 3′-(S-cysteinyl) tyrosine. Differences in the spectroscopic and enzymatic activity have been reported between GlxA and Gox with the indole orientation suggested as a reason. Here, we report a series of in vivo and in vitro studies using the W288F and W288A variants of GlxA to assess the role of Trp288 on the morphology, maturation, spectroscopic and enzymatic properties. Our findings point towards a salient role for Trp288 in the kinetics of copper loading and maturation of GlxA, with its presence essential for stabilising the metalloradical site required for coupling catalytic activity and morphological development.
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Cuzan O, Kochem A, Simaan AJ, Bertaina S, Faure B, Robert V, Shova S, Giorgi M, Maffei M, Réglier M, Orio M. Oxidative DNA Cleavage Promoted by a Phenoxyl‐Radical Copper(II) Complex. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201601001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Olesea Cuzan
- Aix Marseille Université CNRS Centrale Marseille Marseille France
- Institute of Chemistry Academy of Sciences of Moldova 3, Academiei str. MD 2028 Chisinau Republic of Moldova
| | - Amélie Kochem
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | - A. Jalila Simaan
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | | | - Bruno Faure
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | - Viviane Robert
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | - Sergiu Shova
- Institute of Macromolecular Chemistry “Petru Poni” 41A Grigore Ghica Voda Alley 700487 Iasi Romania
| | - Michel Giorgi
- Aix Marseille Univ CNRS Centrale Marseille Marseille France[‡]For his outstanding contribution to inorganic and coordination chemistry
| | - Michel Maffei
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | - Marius Réglier
- Aix Marseille Université CNRS Centrale Marseille Marseille France
| | - Maylis Orio
- Aix Marseille Université CNRS Centrale Marseille Marseille France
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Cowley RE, Cirera J, Qayyum MF, Rokhsana D, Hedman B, Hodgson KO, Dooley DM, Solomon EI. Structure of the Reduced Copper Active Site in Preprocessed Galactose Oxidase: Ligand Tuning for One-Electron O 2 Activation in Cofactor Biogenesis. J Am Chem Soc 2016; 138:13219-13229. [PMID: 27626829 DOI: 10.1021/jacs.6b05792] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Galactose oxidase (GO) is a copper-dependent enzyme that accomplishes 2e- substrate oxidation by pairing a single copper with an unusual cysteinylated tyrosine (Cys-Tyr) redox cofactor. Previous studies have demonstrated that the post-translational biogenesis of Cys-Tyr is copper- and O2-dependent, resulting in a self-processing enzyme system. To investigate the mechanism of cofactor biogenesis in GO, the active-site structure of Cu(I)-loaded GO was determined using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, and density-functional theory (DFT) calculations were performed on this model. Our results show that the active-site tyrosine lowers the Cu potential to enable the thermodynamically unfavorable 1e- reduction of O2, and the resulting Cu(II)-O2•- is activated toward H atom abstraction from cysteine. The final step of biogenesis is a concerted reaction involving coordinated Tyr ring deprotonation where Cu(II) coordination enables formation of the Cys-Tyr cross-link. These spectroscopic and computational results highlight the role of the Cu(I) in enabling O2 activation by 1e- and the role of the resulting Cu(II) in enabling substrate activation for biogenesis.
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Affiliation(s)
- Ryan E Cowley
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Jordi Cirera
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Munzarin F Qayyum
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Dalia Rokhsana
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States
| | - Britt Hedman
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - David M Dooley
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.,University of Rhode Island , Kingston, Rhode Island 02881, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
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Heterologous Production and Characterization of Two Glyoxal Oxidases from Pycnoporus cinnabarinus. Appl Environ Microbiol 2016; 82:4867-75. [PMID: 27260365 PMCID: PMC4968546 DOI: 10.1128/aem.00304-16] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/18/2016] [Indexed: 11/20/2022] Open
Abstract
The genome of the white rot fungus Pycnoporus cinnabarinus includes a large number of genes encoding enzymes implicated in lignin degradation. Among these, three genes are predicted to encode glyoxal oxidase, an enzyme previously isolated from Phanerochaete chrysosporium. The glyoxal oxidase of P. chrysosporium is physiologically coupled to lignin-oxidizing peroxidases via generation of extracellular H2O2 and utilizes an array of aldehydes and α-hydroxycarbonyls as the substrates. Two of the predicted glyoxal oxidases of P. cinnabarinus, GLOX1 (PciGLOX1) and GLOX2 (PciGLOX2), were heterologously produced in Aspergillus niger strain D15#26 (pyrG negative) and purified using immobilized metal ion affinity chromatography, yielding 59 and 5 mg of protein for PciGLOX1 and PciGLOX2, respectively. Both proteins were approximately 60 kDa in size and N-glycosylated. The optimum temperature for the activity of these enzymes was 50°C, and the optimum pH was 6. The enzymes retained most of their activity after incubation at 50°C for 4 h. The highest relative activity and the highest catalytic efficiency of both enzymes occurred with glyoxylic acid as the substrate. The two P. cinnabarinus enzymes generally exhibited similar substrate preferences, but PciGLOX2 showed a broader substrate specificity and was significantly more active on 3-phenylpropionaldehyde.
IMPORTANCE This study addresses the poorly understood role of how fungal peroxidases obtain an in situ supply of hydrogen peroxide to enable them to oxidize a variety of organic and inorganic compounds. This cooperative activity is intrinsic in the living organism to control the amount of toxic H2O2 in its environment, thus providing a feed-on-demand scenario, and can be used biotechnologically to supply a cheap source of peroxide for the peroxidase reaction. The secretion of multiple glyoxal oxidases by filamentous fungi as part of a lignocellulolytic mechanism suggests a controlled system, especially as these enzymes utilize fungal metabolites as the substrates. Two glyoxal oxidases have been isolated and characterized to date, and the differentiation of the substrate specificity of the two enzymes produced by Pycnoporus cinnabarinus illustrates the alternative mechanisms existing in a single fungus, together with the utilization of these enzymes to prepare platform chemicals for industry.
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Kameshwar AKS, Qin W. Lignin Degrading Fungal Enzymes. PRODUCTION OF BIOFUELS AND CHEMICALS FROM LIGNIN 2016. [DOI: 10.1007/978-981-10-1965-4_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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