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Iron homeostasis in the absence of ferricrocin and its consequences in fungal development and insect virulence in Beauveria bassiana. Sci Rep 2021; 11:19624. [PMID: 34608174 PMCID: PMC8490459 DOI: 10.1038/s41598-021-99030-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 09/14/2021] [Indexed: 11/28/2022] Open
Abstract
The putative ferricrocin synthetase gene ferS in the fungal entomopathogen Beauveria bassiana BCC 2660 was identified and characterized. The 14,445-bp ferS encodes a multimodular nonribosomal siderophore synthetase tightly clustered with Fusarium graminearum ferricrocin synthetase. Functional analysis of this gene was performed by disruption with the bar cassette. ΔferS mutants were verified by Southern and PCR analyses. HPLC and TLC analyses of crude extracts indicated that biosynthesis of ferricrocin was abolished in ΔferS. Insect bioassays surprisingly indicated that ΔferS killed the Spodoptera exigua larvae faster (LT50 59 h) than wild type (66 h). Growth and developmental assays of the mutant and wild type demonstrated that ΔferS had a significant increase in germination under iron depletion and radial growth and a decrease in conidiation. Mitotracker staining showed that the mitochondrial activity was enriched in ΔferS under both iron excess and iron depletion. Comparative transcriptomes between wild type and ΔferS indicated that the mutant was increased in the expression of eight cytochrome P450 genes and those in iron homeostasis, ferroptosis, oxidative stress response, ergosterol biosynthesis, and TCA cycle, compared to wild type. Our data suggested that ΔferS sensed the iron excess and the oxidative stress and, in turn, was up-regulated in the antioxidant-related genes and those in ergosterol biosynthesis and TCA cycle. These increased biological pathways help ΔferS grow and germinate faster than the wild type and caused higher insect mortality than the wild type in the early phase of infection.
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Manavalan T, Stepnov AA, Hegnar OA, Eijsink VGH. Sugar oxidoreductases and LPMOs - two sides of the same polysaccharide degradation story? Carbohydr Res 2021; 505:108350. [PMID: 34049079 DOI: 10.1016/j.carres.2021.108350] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/13/2021] [Accepted: 05/14/2021] [Indexed: 12/20/2022]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds in recalcitrant polysaccharides such as chitin and cellulose and their discovery has revolutionized our understanding of enzymatic biomass conversion. The discovery of LPMOs raises interesting new questions regarding the roles of other oxidoreductases and abiotic redox processes in biomass conversion. LPMOs need reducing power and an oxygen co-substrate and biomass degrading ecosystems contain a multitude of redox enzymes that affect the availability of both. For example, biomass degrading fungi produce multiple sugar oxidoreductases whose biological functions so far have remained somewhat enigmatic. It is now conceivable that these redox enzymes, in particular H2O2-producing sugar oxidases, could play a role in fueling and controlling LPMO reactions. Here, we shortly review contemporary issues in the LPMO field, paying particular attention to the possible roles of sugar oxidoreductases.
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Affiliation(s)
- Tamilvendan Manavalan
- Faculty of Chemistry, Biotechnology and Food Science, NMBU - Norwegian University of Life Science, N-1432, Ås, Norway
| | - Anton A Stepnov
- Faculty of Chemistry, Biotechnology and Food Science, NMBU - Norwegian University of Life Science, N-1432, Ås, Norway
| | - Olav A Hegnar
- Faculty of Chemistry, Biotechnology and Food Science, NMBU - Norwegian University of Life Science, N-1432, Ås, Norway
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, NMBU - Norwegian University of Life Science, N-1432, Ås, Norway.
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Gangwar R, Rasool S, Mishra S. Purified cellobiose dehydrogenase of Termitomyces sp. OE147 fuels cellulose degradation resulting in the release of reducing sugars. Prep Biochem Biotechnol 2020; 51:488-496. [PMID: 33063604 DOI: 10.1080/10826068.2020.1833343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Termitomyces sp. OE 147 is one of the active cellulose degraders in the ecosphere and produces large amount of cellobiose dehydrogenase (CDH) and β-glucosidases when cultivated on cellulose. In order to investigate its effect on cellulose, a highly purified preparation of CDH was obtained from the culture supernatant of the fungus cultivated on cellulose. A combination of ultrafiltration, ion-exchange and gel-filtration chromatography was used to purify CDH by ∼172-fold to a high specific activity of ∼324 U/mg protein on lactose which was used for routine measurement of enzyme activity. The enzyme displayed a pH optimum of 5.0 and stability between pH 5.0 and 8.0 with maximum catalytic efficiency (kcat/Km) of 397 mM-1 s-1 on cellobiose. Incubation of microcrystalline cellulose with the purified CDH led to production of reducing sugars which was accelerated by the addition of FeCl3 during the early stages of incubation. A mass spectrometric analysis revealed fragmentation products of cellulose which were concluded to be cellodextrins, sugars, and corresponding aldonic acids suggesting that CDH can release reducing sugars in the absence of externally added lytic polysaccharide monooxygenases. Polymerized products of glucose were also detected at low intensity.
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Affiliation(s)
- Rishabh Gangwar
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India.,School of Biotechnology, Shri Mata Vaishno Devi University, Katra, India
| | - Shafaq Rasool
- School of Biotechnology, Shri Mata Vaishno Devi University, Katra, India
| | - Saroj Mishra
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India
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Protein engineering of cellobiose dehydrogenase from Phanerochaete chrysosporium in yeast Saccharomyces cerevisiae InvSc1 for increased activity and stability. Biochem Eng J 2019. [DOI: 10.1016/j.bej.2019.03.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Evaluation of colorimetric assays for determination of H 2O 2in planta during fungal wood decomposition. J Microbiol Methods 2017; 145:10-13. [PMID: 29242076 DOI: 10.1016/j.mimet.2017.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/08/2017] [Accepted: 12/09/2017] [Indexed: 01/22/2023]
Abstract
Hydrogen peroxide (H2O2) plays a critical role in generating oxygen radicals as fungi attack and deconstruct plant cell walls. Its concentrations in planta, however, are often low during decomposition and evade detection by traditional methods. Here, we compared relevant methods and selected the best based on detection limits and selectivity.
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Chen K, Liu X, Long L, Ding S. Cellobiose dehydrogenase from Volvariella volvacea and its effect on the saccharification of cellulose. Process Biochem 2017. [DOI: 10.1016/j.procbio.2017.05.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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dos Santos HB, Bezerra TMS, Pradella JGC, Delabona P, Lima D, Gomes E, Hartson SD, Rogers J, Couger B, Prade R. Myceliophthora thermophila M77 utilizes hydrolytic and oxidative mechanisms to deconstruct biomass. AMB Express 2016; 6:103. [PMID: 27807811 PMCID: PMC5093097 DOI: 10.1186/s13568-016-0276-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 10/27/2016] [Indexed: 12/23/2022] Open
Abstract
Biomass is abundant, renewable and useful for biofuel production as well as chemical priming for plastics and composites. Deconstruction of biomass by enzymes is perceived as recalcitrant while an inclusive breakdown mechanism remains to be discovered. Fungi such as Myceliophthora thermophila M77 appear to decompose natural biomass sources quite well. This work reports on this fungus fermentation property while producing cellulolytic enzymes using natural biomass substrates. Little hydrolytic activity was detected, insufficient to explain the large amount of biomass depleted in the process. Furthermore, this work makes a comprehensive account of extracellular proteins and describes how secretomes redirect their qualitative protein content based on the nature and chemistry of the nutritional source. Fungus grown on purified cellulose or on natural biomass produced secretomes constituted by: cellobiohydrolases, cellobiose dehydrogenase, β-1,3 glucanase, β-glucosidases, aldose epimerase, glyoxal oxidase, GH74 xyloglucanase, galactosidase, aldolactonase and polysaccharide monooxygenases. Fungus grown on a mixture of purified hemicellulose fractions (xylans, arabinans and arabinoxylans) produced many enzymes, some of which are listed here: xylosidase, mixed β-1,3(4) glucanase, β-1,3 glucanases, β-glucosidases, β-mannosidase, β-glucosidases, galactosidase, chitinases, polysaccharide lyase, endo β-1,6 galactanase and aldose epimerase. Secretomes produced on natural biomass displayed a comprehensive set of enzymes involved in hydrolysis and oxidation of cellulose, hemicellulose-pectin and lignin. The participation of oxidation reactions coupled to lignin decomposition in the breakdown of natural biomass may explain the discrepancy observed for cellulose decomposition in relation to natural biomass fermentation experiments.
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Zhang MF, Qin YH, Ma JY, Yang L, Wu ZK, Wang TL, Wang WG, Wang CW. Depolymerization of microcrystalline cellulose by the combination of ultrasound and Fenton reagent. ULTRASONICS SONOCHEMISTRY 2016; 31:404-8. [PMID: 26964965 DOI: 10.1016/j.ultsonch.2016.01.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 01/25/2016] [Accepted: 01/25/2016] [Indexed: 05/20/2023]
Abstract
In this study, the combined use of Fenton reagent and ultrasound to the pretreatment of microcrystalline cellulose (MCC) for subsequent enzyme hydrolysis was investigated. The morphological analysis showed that the aspect ratio of MCC was greatly reduced after pretreatment. The X-ray diffraction (XRD) and degree of polymerization (DP) analyses showed that Fenton reagent was more efficient in decreasing the crystallinity of MCC while ultrasound was more efficient in decreasing the DP of MCC. The combination of Fenton reaction and ultrasound, which produced the lowest crystallinity (84.8 ± 0.2%) and DP (124.7 ± 0.6) of MCC and the highest yield of reducing sugar (22.9 ± 0.3 g/100 g), provides a promising pretreatment process for MCC depolymerization.
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Affiliation(s)
- Mei-Fang Zhang
- Key Laboratory of Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Yuan-Hang Qin
- Key Laboratory of Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China.
| | - Jia-Yu Ma
- Key Laboratory of Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Li Yang
- Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Zai-Kun Wu
- Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Tie-Lin Wang
- Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Wei-Guo Wang
- Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China
| | - Cun-Wen Wang
- Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, China.
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Gene Expression Patterns of Wood Decay Fungi Postia placenta and Phanerochaete chrysosporium Are Influenced by Wood Substrate Composition during Degradation. Appl Environ Microbiol 2016; 82:4387-4400. [PMID: 27208101 DOI: 10.1128/aem.00134-16] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 05/08/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Identification of the specific genes and enzymes involved in the fungal degradation of lignocellulosic biomass derived from feedstocks with various compositions is essential to the development of improved bioenergy processes. In order to elucidate the effect of substrate composition on gene expression in wood-rotting fungi, we employed microarrays based on the annotated genomes of the brown- and white-rot fungi, Rhodonia placenta (formerly Postia placenta) and Phanerochaete chrysosporium, respectively. We monitored the expression of genes involved in the enzymatic deconstruction of the cell walls of three 4-year-old Populus trichocarpa (poplar) trees of genotypes with distinct cell wall chemistries, selected from a population of several hundred trees grown in a common garden. The woody substrates were incubated with wood decay fungi for 10, 20, and 30 days. An analysis of transcript abundance in all pairwise comparisons highlighted 64 and 84 differentially expressed genes (>2-fold, P < 0.05) in P. chrysosporium and P. placenta, respectively. Cross-fungal comparisons also revealed an array of highly differentially expressed genes (>4-fold, P < 0.01) across different substrates and time points. These results clearly demonstrate that gene expression profiles of P. chrysosporium and P. placenta are influenced by wood substrate composition and the duration of incubation. Many of the significantly expressed genes encode "proteins of unknown function," and determining their role in lignocellulose degradation presents opportunities and challenges for future research. IMPORTANCE This study describes the variation in expression patterns of two wood-degrading fungi (brown- and white-rot fungi) during colonization and incubation on three different naturally occurring poplar substrates of differing chemical compositions, over time. The results clearly show that the two fungi respond differentially to their substrates and that several known and, more interestingly, currently unknown genes are highly misregulated in response to various substrate compositions. These findings highlight the need to characterize several unknown proteins for catalytic function but also as potential candidate proteins to improve the efficiency of enzymatic cocktails to degrade lignocellulosic substrates in industrial applications, such as in a biochemically based bioenergy platform.
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Hildebrand A, Bennett Addison J, Kasuga T, Fan Z. Cellobionic acid inhibition of cellobiohydrolase I and cellobiose dehydrogenase. Biochem Eng J 2016. [DOI: 10.1016/j.bej.2016.01.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
SUMMARY Biomass is constructed of dense recalcitrant polymeric materials: proteins, lignin, and holocellulose, a fraction constituting fibrous cellulose wrapped in hemicellulose-pectin. Bacteria and fungi are abundant in soil and forest floors, actively recycling biomass mainly by extracting sugars from holocellulose degradation. Here we review the genome-wide contents of seven Aspergillus species and unravel hundreds of gene models encoding holocellulose-degrading enzymes. Numerous apparent gene duplications followed functional evolution, grouping similar genes into smaller coherent functional families according to specialized structural features, domain organization, biochemical activity, and genus genome distribution. Aspergilli contain about 37 cellulase gene models, clustered in two mechanistic categories: 27 hydrolyze and 10 oxidize glycosidic bonds. Within the oxidative enzymes, we found two cellobiose dehydrogenases that produce oxygen radicals utilized by eight lytic polysaccharide monooxygenases that oxidize glycosidic linkages, breaking crystalline cellulose chains and making them accessible to hydrolytic enzymes. Among the hydrolases, six cellobiohydrolases with a tunnel-like structural fold embrace single crystalline cellulose chains and cooperate at nonreducing or reducing end termini, splitting off cellobiose. Five endoglucanases group into four structural families and interact randomly and internally with cellulose through an open cleft catalytic domain, and finally, seven extracellular β-glucosidases cleave cellobiose and related oligomers into glucose. Aspergilli contain, on average, 30 hemicellulase and 7 accessory gene models, distributed among 9 distinct functional categories: the backbone-attacking enzymes xylanase, mannosidase, arabinase, and xyloglucanase, the short-side-chain-removing enzymes xylan α-1,2-glucuronidase, arabinofuranosidase, and xylosidase, and the accessory enzymes acetyl xylan and feruloyl esterases.
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12
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Bashir H, Gangwar R, Mishra S. Differential production of lignocellulolytic enzymes by a white rot fungus Termitomyces sp. OE147 on cellulose and lactose. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1290-9. [PMID: 26164778 DOI: 10.1016/j.bbapap.2015.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 07/03/2015] [Accepted: 07/06/2015] [Indexed: 01/10/2023]
Abstract
White-rot fungi are the only organisms known to degrade all basic wood polymers using different strategies of employing a variety of hydrolytic and oxidative enzymes. A comparative secretome analysis of Termitomyces sp. OE147 cultivated on cellulose and lactose was carried out by two-dimensional gel electrophoresis followed by MALDI-TOF/TOF-MS analysis to identify the enzymes coordinately expressed on cellulose. A total of 29 proteins, belonging to CAZy hydrolases (11), CAZy oxidoreductases (13) and some 'other' (5) proteins were identified. Among the CAZy hydrolases, a distinct repertoire of cellulolytic and hemicellulolytic enzymes were produced while among the CAZy oxidoreductases, cellobiose dehydrogenase and laccase were the predominant enzymes along with H2O2 dependent peroxidases. This coordinated expression indicated a unique and integrated system for degradation of not only crystalline cellulose but also other components of lignocellulolytic substrates, namely lignin and xylan. Activities of the identified proteins were confirmed by plate assays and activity measurements. Many of the enzyme activities were also correlated with reduction in the crystallinity index of cellulose. Based on the enhanced production of CDH, β-glucosidases and several oxidoreductases, a more prominent role of these enzymes is indicated in this fungus in cellulose breakdown.
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Affiliation(s)
- Humayra Bashir
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Rishabh Gangwar
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Saroj Mishra
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi 110016, India.
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Influence of Populus genotype on gene expression by the wood decay fungus Phanerochaete chrysosporium. Appl Environ Microbiol 2014; 80:5828-35. [PMID: 25015893 DOI: 10.1128/aem.01604-14] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We examined gene expression patterns in the lignin-degrading fungus Phanerochaete chrysosporium when it colonizes hybrid poplar (Populus alba × tremula) and syringyl (S)-rich transgenic derivatives. A combination of microarrays and liquid chromatography-tandem mass spectrometry (LC-MS/MS) allowed detection of a total of 9,959 transcripts and 793 proteins. Comparisons of P. chrysosporium transcript abundance in medium containing poplar or glucose as a sole carbon source showed 113 regulated genes, 11 of which were significantly higher (>2-fold, P < 0.05) in transgenic line 64 relative to the parental line. Possibly related to the very large amounts of syringyl (S) units in this transgenic tree (94 mol% S), several oxidoreductases were among the upregulated genes. Peptides corresponding to a total of 18 oxidoreductases were identified in medium consisting of biomass from line 64 or 82 (85 mol% S) but not in the parental clone (65 mol% S). These results demonstrate that P. chrysosporium gene expression patterns are substantially influenced by lignin composition.
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Nakagame S, Furujyo A, Sugiura J. Purification and Characterization of Cellobiose Dehydrogenase from White-Rot BasidiomyceteTrametes hirsuta. Biosci Biotechnol Biochem 2014; 70:1629-35. [PMID: 16861797 DOI: 10.1271/bbb.50692] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In order to save energy during the pulp making process, we tried to use white-rot basidiomycete, Trametes hirsuta, which degrades lignin efficiently. But a decrease in paper strength caused by cellulolytic activity ruled this out for practical application. Since the cellulolytic activity of the fungus must be decreased, we purified and characterized a cellobiose dehydrogenase (CDH) that was reported to damage pulp fiber. The CDH in the culture filtrate of C. hirsutus was purified by freeze-thawing and chromatographic methods. The pI of the enzyme was 4.2 and its molecular weight was 92 kDa. The optimal temperature and pH of the enzyme were 60-70 degrees C and 5.0 respectively. Since the purified CDH decreased the viscosity of pulp in the presence of Fe(III) and cellobiose, it was shown that the suppression of CDH should be an effective way to reduce cellulose damage.
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Affiliation(s)
- Seiji Nakagame
- Technological Initiatives Research Laboratory, Oji Paper Co., Ltd., Tokyo 135-8558, Japan
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Proskurina OV, Korotkova OG, Rozhkova AM, Matys VY, Koshelev AV, Okunev ON, Nemashkalov VA, Sinitsyna OA, Revin VV, Sinitsyn AP. Trichoderma reesei endoglucanase IV: A new component of biocatalysts based on the cellulase complex of the fungus Penicillium verruculosum for hydrolysis of cellulose-containing biomass. CATALYSIS IN INDUSTRY 2014. [DOI: 10.1134/s2070050414010085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Temporal alterations in the secretome of the selective ligninolytic fungus Ceriporiopsis subvermispora during growth on aspen wood reveal this organism's strategy for degrading lignocellulose. Appl Environ Microbiol 2014; 80:2062-70. [PMID: 24441164 DOI: 10.1128/aem.03652-13] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The white-rot basidiomycetes efficiently degrade all wood cell wall polymers. Generally, these fungi simultaneously degrade cellulose and lignin, but certain organisms, such as Ceriporiopsis subvermispora, selectively remove lignin in advance of cellulose degradation. However, relatively little is known about the mechanism of selective ligninolysis. To address this issue, C. subvermispora was grown in liquid medium containing ball-milled aspen, and nano-liquid chromatography-tandem mass spectrometry was used to identify and estimate extracellular protein abundance over time. Several manganese peroxidases and an aryl alcohol oxidase, both associated with lignin degradation, were identified after 3 days of incubation. A glycoside hydrolase (GH) family 51 arabinofuranosidase was also identified after 3 days but then successively decreased in later samples. Several enzymes related to cellulose and xylan degradation, such as GH10 endoxylanase, GH5_5 endoglucanase, and GH7 cellobiohydrolase, were detected after 5 days. Peptides corresponding to potential cellulose-degrading enzymes GH12, GH45, lytic polysaccharide monooxygenase, and cellobiose dehydrogenase were most abundant after 7 days. This sequential production of enzymes provides a mechanism consistent with selective ligninolysis by C. subvermispora.
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Sulej J, Janusz G, Osińska-Jaroszuk M, Małek P, Mazur A, Komaniecka I, Choma A, Rogalski J. Characterization of cellobiose dehydrogenase and its FAD-domain from the ligninolytic basidiomycete Pycnoporus sanguineus. Enzyme Microb Technol 2013; 53:427-37. [PMID: 24315647 DOI: 10.1016/j.enzmictec.2013.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 09/16/2013] [Accepted: 09/17/2013] [Indexed: 10/26/2022]
Abstract
Cellobiose dehydrogenase (CDH), an extracellular flavocytochrome produced by several wood-degrading fungi, was detected in the culture supernatant of the selective delignifier Pycnoporus sanguineus maintained on a cellulose-based liquid medium. Cellobiose dehydrogenase was purified as two active fractions: CDH1-FAD (flavin domain) (40.4 fold) with recovery of 10.9% and CDH1 (flavo-heme enzyme) (54.7 fold) with recovery of 9.8%. As determined by SDS-PAGE, the molecular mass of the purified enzyme was found to be 113.4kDa and its isoelectric point was 4.2, whereas these values for the FAD-domain were 82.7kDa and pI=6.7. The carbohydrate content of the purified enzymes was 9.2%. In this work, the cellobiose dehydrogenase gene cdh1 and its corresponding cDNA from fungus P. sanguineus were isolated, cloned, and characterized. The 2310bp full-length cDNA of cdh1 encoded a mature CDH protein containing 769 amino acids, which was preceded by a signal peptide of 19 amino acids. Moreover, both active fractions were characterized in terms of kinetics, temperature and pH optima, and antioxidant properties.
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Affiliation(s)
- Justyna Sulej
- Department of Biochemistry, Maria Curie-Skłodowska University, Akademicka 19 St., 20-033 Lublin, Poland
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Flory AR, Vicuna Requesens D, Devaiah SP, Teoh KT, Mansfield SD, Hood EE. Development of a green binder system for paper products. BMC Biotechnol 2013; 13:28. [PMID: 23531016 PMCID: PMC3644241 DOI: 10.1186/1472-6750-13-28] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 03/18/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND It is important for industries to find green chemistries for manufacturing their products that have utility, are cost-effective and that protect the environment. The paper industry is no exception. Renewable resources derived from plant components could be an excellent substitute for the chemicals that are currently used as paper binders. Air laid pressed paper products that are typically used in wet wipes must be bound together so they can resist mechanical tearing during storage and use. The binders must be strong but cost-effective. Although chemical binders are approved by the Environmental Protection Agency, the public is demanding products with lower carbon footprints and that are derived from renewable sources. RESULTS In this project, carbohydrates, proteins and phenolic compounds were applied to air laid, pressed paper products in order to identify potential renewable green binders that are as strong as the current commercial binders, while being organic and renewable. Each potential green binder was applied to several filter paper strips and tested for strength in the direction perpendicular to the cellulose fibril orientation. Out of the twenty binders surveyed, soy protein, gelatin, zein protein, pectin and Salix lignin provided comparable strength results to a currently employed chemical binder. CONCLUSIONS These organic and renewable binders can be purchased in large quantities at low cost, require minimal reaction time and do not form viscous solutions that would clog sprayers, characteristics that make them attractive to the non-woven paper industry. As with any new process, a large-scale trial must be conducted along with an economic analysis of the procedure. However, because multiple examples of "green" binders were found that showed strong cross-linking activity, a candidate for commercial application will likely be found.
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Affiliation(s)
- Ashley R Flory
- Arkansas Biosciences Institute, Arkansas State University, Jonesboro, AR 72467, USA
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Syringyl-rich lignin renders poplars more resistant to degradation by wood decay fungi. Appl Environ Microbiol 2013; 79:2560-71. [PMID: 23396333 DOI: 10.1128/aem.03182-12] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In order to elucidate the effects of lignin composition on the resistance of wood to degradation by decay fungi, wood specimens from two transgenic poplar lines expressing an Arabidopsis gene encoding ferulate 5-hydroxylase (F5H) driven by the cinnimate-4-hydroxylase promoter (C4H::F5H) that increased syringyl/guaiacyl (S/G) monolignol ratios relative to those in the untransformed control wood were incubated with six different wood decay fungi. Alterations in wood weight and chemical composition were monitored over the incubation period. The results showed that transgenic poplar lines extremely rich in syringyl lignin exhibited a drastically improved resistance to degradation by all decay fungi evaluated. Lignin monomer composition and its distribution among cell types and within different cell layers were the sole wood chemistry parameters determining wood durability. Since transgenic poplars with exceedingly high syringyl contents were recalcitrant to degradation, where wood durability is a critical factor, these genotypes may offer improved performance.
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van der Lelie D, Taghavi S, McCorkle SM, Li LL, Malfatti SA, Monteleone D, Donohoe BS, Ding SY, Adney WS, Himmel ME, Tringe SG. The metagenome of an anaerobic microbial community decomposing poplar wood chips. PLoS One 2012; 7:e36740. [PMID: 22629327 PMCID: PMC3357426 DOI: 10.1371/journal.pone.0036740] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Accepted: 04/11/2012] [Indexed: 02/01/2023] Open
Abstract
This study describes the composition and metabolic potential of a lignocellulosic biomass degrading community that decays poplar wood chips under anaerobic conditions. We examined the community that developed on poplar biomass in a non-aerated bioreactor over the course of a year, with no microbial inoculation other than the naturally occurring organisms on the woody material. The composition of this community contrasts in important ways with biomass-degrading communities associated with higher organisms, which have evolved over millions of years into a symbiotic relationship. Both mammalian and insect hosts provide partial size reduction, chemical treatments (low or high pH environments), and complex enzymatic ‘secretomes’ that improve microbial access to cell wall polymers. We hypothesized that in order to efficiently degrade coarse untreated biomass, a spontaneously assembled free-living community must both employ alternative strategies, such as enzymatic lignin depolymerization, for accessing hemicellulose and cellulose and have a much broader metabolic potential than host-associated communities. This would suggest that such a community would make a valuable resource for finding new catalytic functions involved in biomass decomposition and gaining new insight into the poorly understood process of anaerobic lignin depolymerization. Therefore, in addition to determining the major players in this community, our work specifically aimed at identifying functions potentially involved in the depolymerization of cellulose, hemicelluloses, and lignin, and to assign specific roles to the prevalent community members in the collaborative process of biomass decomposition. A bacterium similar to Magnetospirillum was identified among the dominant community members, which could play a key role in the anaerobic breakdown of aromatic compounds. We suggest that these compounds are released from the lignin fraction in poplar hardwood during the decay process, which would point to lignin-modification or depolymerization under anaerobic conditions.
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Affiliation(s)
- Daniel van der Lelie
- Biology Department, Brookhaven National Laboratory, Upton, New York, United States of America.
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Efficient immobilization technique for enhancement of cellobiose dehydrogenase activity on silica gel. BIOTECHNOL BIOPROC E 2012. [DOI: 10.1007/s12257-011-0085-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Santhanam N, Badri DV, Decker SR, Manter DK, Reardon KF, Vivanco JM. Lignocellulose Decomposition by Microbial Secretions. SIGNALING AND COMMUNICATION IN PLANTS 2012. [DOI: 10.1007/978-3-642-23047-9_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Canam T, Town JR, Tsang A, McAllister TA, Dumonceaux TJ. Biological pretreatment with a cellobiose dehydrogenase-deficient strain of Trametes versicolor enhances the biofuel potential of canola straw. BIORESOURCE TECHNOLOGY 2011; 102:10020-10027. [PMID: 21903381 DOI: 10.1016/j.biortech.2011.08.045] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 08/08/2011] [Accepted: 08/10/2011] [Indexed: 05/31/2023]
Abstract
The use of Trametes versicolor as a biological pretreatment for canola straw was explored in the context of biofuel production. Specifically, the effects on the straw of a wild-type strain (52J) and a cellobiose dehydrogenase (CDH)-deficient strain (m4D) were investigated. The xylose and glucose contents of the straw treated with 52J were significantly reduced, while only the xylose content was reduced with m4D treatment. Lignin extractability was greatly improved with fungal treatments compared to untreated straw. Saccharification of the residue of the m4D-treated straw led to a significant increase in proportional glucose yield, which was partially attributed to the lack of cellulose catabolism by m4D. Overall, the results of this study indicate that CDH facilitates cellulose access by T. versicolor. Furthermore, treatment of lignocellulosic material with m4D offers improvements in lignin extractability and saccharification efficacy compared to untreated biomass without loss of substrate due to fungal catabolism.
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Affiliation(s)
- Thomas Canam
- Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK, Canada
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Enhanced production of cellobiose dehydrogenase and β-glucosidase by Phanerochaete chrysosporium. KOREAN J CHEM ENG 2011. [DOI: 10.1007/s11814-011-0144-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Significant alteration of gene expression in wood decay fungi Postia placenta and Phanerochaete chrysosporium by plant species. Appl Environ Microbiol 2011; 77:4499-507. [PMID: 21551287 DOI: 10.1128/aem.00508-11] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Identification of specific genes and enzymes involved in conversion of lignocellulosics from an expanding number of potential feedstocks is of growing interest to bioenergy process development. The basidiomycetous wood decay fungi Phanerochaete chrysosporium and Postia placenta are promising in this regard because they are able to utilize a wide range of simple and complex carbon compounds. However, systematic comparative studies with different woody substrates have not been reported. To address this issue, we examined gene expression of these fungi colonizing aspen (Populus grandidentata) and pine (Pinus strobus). Transcript levels of genes encoding extracellular glycoside hydrolases, thought to be important for hydrolytic cleavage of hemicelluloses and cellulose, showed little difference for P. placenta colonizing pine versus aspen as the sole carbon source. However, 164 genes exhibited significant differences in transcript accumulation for these substrates. Among these, 15 cytochrome P450s were upregulated in pine relative to aspen. Of 72 P. placenta extracellular proteins identified unambiguously by mass spectrometry, 52 were detected while colonizing both substrates and 10 were identified in pine but not aspen cultures. Most of the 178 P. chrysosporium glycoside hydrolase genes showed similar transcript levels on both substrates, but 13 accumulated >2-fold higher levels on aspen than on pine. Of 118 confidently identified proteins, 31 were identified in both substrates and 57 were identified in pine but not aspen cultures. Thus, P. placenta and P. chrysosporium gene expression patterns are influenced substantially by wood species. Such adaptations to the carbon source may also reflect fundamental differences in the mechanisms by which these fungi attack plant cell walls.
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Zeng G, Li Z, Tang L, Wu M, Lei X, Liu Y, Liu C, Pang Y, Zhang Y. Gold nanoparticles/water-soluble carbon nanotubes/aromatic diamine polymer composite films for highly sensitive detection of cellobiose dehydrogenase gene. Electrochim Acta 2011. [DOI: 10.1016/j.electacta.2011.03.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Harreither W, Sygmund C, Augustin M, Narciso M, Rabinovich ML, Gorton L, Haltrich D, Ludwig R. Catalytic properties and classification of cellobiose dehydrogenases from ascomycetes. Appl Environ Microbiol 2011; 77:1804-15. [PMID: 21216904 PMCID: PMC3067291 DOI: 10.1128/aem.02052-10] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 12/23/2010] [Indexed: 12/26/2022] Open
Abstract
Putative cellobiose dehydrogenase (CDH) genes are frequently discovered in various fungi by genome sequencing projects. The expression of CDH, an extracellular flavocytochrome, is well studied in white rot basidiomycetes and is attributed to extracellular lignocellulose degradation. CDH has also been reported for plant-pathogenic or saprotrophic ascomycetes, but the molecular and catalytic properties of these enzymes are currently less investigated. This study links various ascomycetous cdh genes with the molecular and catalytic characteristics of the mature proteins and suggests a differentiation of ascomycete class II CDHs into two subclasses, namely, class IIA and class IIB, in addition to the recently introduced class III of hypothetical ascomycete CDHs. This new classification is based on sequence and biochemical data obtained from sequenced fungal genomes and a screening of 40 ascomycetes. Thirteen strains showed CDH activity when they were grown on cellulose-based media, and Chaetomium atrobrunneum, Corynascus thermophilus, Dichomera saubinetii, Hypoxylon haematostroma, Neurospora crassa, and Stachybotrys bisbyi were selected for detailed studies. In these strains, one or two cdh-encoding genes were found that stem either from class IIA and contain a C-terminal carbohydrate-binding module or from class IIB without such a module. In several strains, both genes were found. Regarding substrate specificity, class IIB CDHs show a less pronounced substrate specificity for cellobiose than class IIA enzymes. A pH-dependent pattern of the intramolecular electron transfer was also observed, and the CDHs were classified into three groups featuring acidic, intermediate, or alkaline pH optima. The pH optimum, however, does not correlate with the CDH subclasses and is most likely a species-dependent adaptation to different habitats.
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Affiliation(s)
- Wolfgang Harreither
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Christoph Sygmund
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Manfred Augustin
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Melanie Narciso
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Mikhail L. Rabinovich
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Lo Gorton
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Dietmar Haltrich
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Roland Ludwig
- Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia, Department of Analytical Chemistry/Biochemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
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Kim EJ, Kang SW, Song KH, Han SO, Kim JJ, Kim SW. Improvement of Cellobiose Dehydrogenase(CDH) and β-Glucosidase Activity by Phanerochaete chrysosporium Mutant. KOREAN CHEMICAL ENGINEERING RESEARCH 2011. [DOI: 10.9713/kcer.2011.49.1.101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Zhang R, Fan Z, Kasuga T. Expression of cellobiose dehydrogenase from Neurospora crassa in Pichia pastoris and its purification and characterization. Protein Expr Purif 2011; 75:63-9. [DOI: 10.1016/j.pep.2010.08.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2010] [Revised: 08/10/2010] [Accepted: 08/10/2010] [Indexed: 10/19/2022]
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Ludwig R, Harreither W, Tasca F, Gorton L. Cellobiose Dehydrogenase: A Versatile Catalyst for Electrochemical Applications. Chemphyschem 2010; 11:2674-97. [DOI: 10.1002/cphc.201000216] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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31
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Mowat CG, Gazur B, Campbell LP, Chapman SK. Flavin-containing heme enzymes. Arch Biochem Biophys 2010; 493:37-52. [DOI: 10.1016/j.abb.2009.10.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/13/2009] [Accepted: 10/13/2009] [Indexed: 11/25/2022]
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Production of oligosaccharides and cellobionic acid by Fibrobacter succinogenes S85 growing on sugars, cellulose and wheat straw. Appl Microbiol Biotechnol 2009; 83:425-33. [DOI: 10.1007/s00253-009-1884-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 01/19/2009] [Accepted: 01/19/2009] [Indexed: 10/21/2022]
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Vanden Wymelenberg A, Sabat G, Mozuch M, Kersten PJ, Cullen D, Blanchette RA. Structure, organization, and transcriptional regulation of a family of copper radical oxidase genes in the lignin-degrading basidiomycete Phanerochaete chrysosporium. Appl Environ Microbiol 2006; 72:4871-7. [PMID: 16820482 PMCID: PMC1489383 DOI: 10.1128/aem.00375-06] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The white rot basidiomycete Phanerochaete chrysosporium produces an array of nonspecific extracellular enzymes thought to be involved in lignin degradation, including lignin peroxidases, manganese peroxidases, and the H2O2-generating copper radical oxidase, glyoxal oxidase (GLX). Preliminary analysis of the P. chrysosporium draft genome had identified six sequences with significant similarity to GLX and designated cro1 through cro6. The predicted mature protein sequences diverge substantially from one another, but the residues coordinating copper and constituting the radical redox site are conserved. Transcript profiles, microscopic examination, and lignin analysis of inoculated thin wood sections are consistent with differential regulation as decay advances. The cro2-encoded protein was detected by liquid chromatography-tandem mass spectrometry in defined medium. The cro2 cDNA was successfully expressed in Aspergillus nidulans under the control of the A. niger glucoamylase promoter and secretion signal. The recombinant CRO2 protein had a substantially different substrate preference than GLX. The role of structurally and functionally diverse cro genes in lignocellulose degradation remains to be established.
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Affiliation(s)
- Amber Vanden Wymelenberg
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
| | - Grzegorz Sabat
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
| | - Michael Mozuch
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
| | - Philip J. Kersten
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
| | - Dan Cullen
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
- Corresponding author. Mailing address: Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53726. Phone: (608) 231-9468. Fax: (608) 231-9262. E-mail:
| | - Robert A. Blanchette
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, Genetics and Biotechnology Center, University of Wisconsin, Madison, Wisconsin 53706, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108
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Wymelenberg AV, Sabat G, Martinez D, Rajangam AS, Teeri TT, Gaskell J, Kersten PJ, Cullen D. The Phanerochaete chrysosporium secretome: Database predictions and initial mass spectrometry peptide identifications in cellulose-grown medium. J Biotechnol 2005; 118:17-34. [PMID: 15888348 DOI: 10.1016/j.jbiotec.2005.03.010] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2004] [Revised: 03/03/2005] [Accepted: 03/26/2005] [Indexed: 11/28/2022]
Abstract
The white rot basidiomycete, Phanerochaete chrysosporium, employs an array of extracellular enzymes to completely degrade the major polymers of wood: cellulose, hemicellulose and lignin. Towards the identification of participating enzymes, 268 likely secreted proteins were predicted using SignalP and TargetP algorithms. To assess the reliability of secretome predictions and to evaluate the usefulness of the current database, we performed shotgun LC-MS/MS on cultures grown on standard cellulose-containing medium. A total of 182 unique peptide sequences were matched to 50 specific genes, of which 24 were among the secretome subset. Underscoring the rich genetic diversity of P. chrysosporium, identifications included 32 glycosyl hydrolases. Functionally interconnected enzyme groups were recognized. For example, the multiple endoglucanases and processive exocellobiohydrolases observed quite probably attack cellulose in a synergistic manner. In addition, a hemicellulolytic system included endoxylanases, alpha-galactosidase, acetyl xylan esterase, and alpha-l-arabinofuranosidase. Glucose and cellobiose metabolism likely involves cellobiose dehydrogenase, glucose oxidase, and various inverting glycoside hydrolases, all perhaps enhanced by an epimerase. To evaluate the completeness of the current database, mass spectroscopy analysis was performed on a larger and more inclusive dataset containing all possible ORFs. This allowed identification of a previously undetected hypothetical protein and a putative acid phosphatase. The expression of several genes was supported by RT-PCR amplification of their cDNAs.
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Wingate KG, Stuthridge T, Mansfield SD. Colour remediation of pulp mill effluent using purified fungal cellobiose dehydrogenase: Reaction optimisation and mechanism of degradation. Biotechnol Bioeng 2005; 90:95-106. [PMID: 15726583 DOI: 10.1002/bit.20419] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cellobiose dehydrogenase purified from two different fungal sources was assessed for its ability to remove and/or reduce colour from pulp mill bleach plant effluent. Cellobiose dehydrogenase purified from Phanerochaete chrysosporium was shown to prefer acidic conditions and was consequently used to treat the acid effluent stream discharged from a pulp mill bleach plant, while an analogous enzyme originating from Humicola insolens preferred alkaline conditions, and was applied to the effluent discharged from the caustic sewer of the bleach plant. Both enzyme preparations were able to remove colour from their respective effluent sources to a comparable extent. Up to 50% of the effluent colour was removed within 4 days when treated under optimised conditions. Furthermore, it was also shown that this enzymatic approach was effective at removing colour generated by both softwood and hardwood resources. Mechanistically, it was shown that colour was removed from all molecular weight fractions, and the higher molecular weight material (>300 kDa) was concurrently preferentially degraded. Cellobiose dehydrogenase treatment of effluent did not target phenolic, stilbene, or alpha-carbonyl structures, but did affect the quinone content. Further investigations using model compounds confirmed these results, and subsequently showed that only the para-quinones with low substitution were reduced with cellobiose dehydrogenase.
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Hallberg BM, Henriksson G, Pettersson G, Vasella A, Divne C. Mechanism of the reductive half-reaction in cellobiose dehydrogenase. J Biol Chem 2003; 278:7160-6. [PMID: 12493734 DOI: 10.1074/jbc.m210961200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The extracellular flavocytochrome cellobiose dehydrogenase (CDH; EC ) participates in lignocellulose degradation by white-rot fungi with a proposed role in the early events of wood degradation. The complete hemoflavoenzyme consists of a catalytically active dehydrogenase fragment (DH(cdh)) connected to a b-type cytochrome domain via a linker peptide. In the reductive half-reaction, DH(cdh) catalyzes the oxidation of cellobiose to yield cellobiono-1,5-lactone. The active site of DH(cdh) is structurally similar to that of glucose oxidase and cholesterol oxidase, with a conserved histidine residue positioned at the re face of the flavin ring close to the N5 atom. The mechanisms of oxidation in glucose oxidase and cholesterol oxidase are still poorly understood, partly because of lack of experimental structure data or difficulties in interpreting existing data for enzyme-ligand complexes. Here we report the crystal structure of the Phanerochaete chrysosporium DH(cdh) with a bound inhibitor, cellobiono-1,5-lactam, at 1.8-A resolution. The distance between the lactam C1 and the flavin N5 is only 2.9 A, implying that in an approximately planar transition state, the maximum distance for the axial 1-hydrogen to travel for covalent addition to N5 is 0.8-0.9 A. The lactam O1 interacts intimately with the side chains of His-689 and Asn-732. Our data lend substantial structural support to a reaction mechanism where His-689 acts as a general base by abstracting the O1 hydroxyl proton in concert with transfer of the C1 hydrogen as hydride to the re face of the flavin N5.
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Affiliation(s)
- B Martin Hallberg
- Department of Biotechnology, Albanova University Center, KTH, SE-106 91 Stockholm, Sweden
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Rotsaert FA, Li B, Renganathan V, Gold MH. Site-directed mutagenesis of the heme axial ligands in the hemoflavoenzyme cellobiose dehydrogenase. Arch Biochem Biophys 2001; 390:206-14. [PMID: 11396923 DOI: 10.1006/abbi.2001.2362] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium is an extracellular 90-kDa hemoflavoenzyme, organized into an N-terminal heme domain and a C-terminal flavin domain. The amino acid residues Met65 and His114 or His163 were suggested to be heme iron ligands. Mutations of these residues were made and mutant proteins were characterized. H114A mutant cultures produce a stable hemoflavoenzyme with spectral and kinetic characteristics similar to those of wild-type CDH. The M65A and H163A transformants secrete a 90-kDa hemoflavoenzyme, which oxidizes cellobiose in the presence of 2,6-dichlorophenol-indophenol (DCPIP), but is unable to reduce cytochrome c. The heme domains of the M65A and H163A CDH variants are, however, unstable and susceptible to degradation, both yielding a 70-kDa cellobiose-oxidizing flavoenzyme. The spectral and kinetic characteristics of these truncated variants suggest that they contain only their respective flavin domains. The yield of the 90-kDa proteins was low and the proteins could not be purified to homogeneity; however, absorption spectra indicate that the 90-kDa proteins do contain the heme domain. Like the truncated flavoenzymes, the 90-kDa variants reduce DCPIP but are unable to transfer electrons to cytochrome c, in contrast to wild-type CDH. These findings suggest that H163 and M65 are the axial heme ligands and that both ligands are required for the reactivity and structural integrity of the heme domain.
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Affiliation(s)
- F A Rotsaert
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, Beaverton, Oregon 97006-8921, USA
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Cameron MD, Aust SD. Cellobiose dehydrogenase-an extracellular fungal flavocytochrome. Enzyme Microb Technol 2001; 28:129-138. [PMID: 11166803 DOI: 10.1016/s0141-0229(00)00307-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Wood-degrading fungi, including white-rot and soft-rot fungi as well as at least one brown-rot fungus, produce cellobiose dehydrogenase (CDH). CDH has generated recent interest because of its ability to facilitate the formation of free radicals and because it makes a nice model to study intraprotein electron transfer. While the physiological function of CDH is not known, a considerable portion of this review discusses the strength of the data dealing with individual hypotheses. New evidence dealing with proteolysis of CDH in relationship to the interaction of CDH with lignin and manganese peroxidases are discussed. Additionally, recent information dealing with the catalytic mechanism and reactivity of the individual domains of CDH is detailed.
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Affiliation(s)
- M D. Cameron
- Biotechnology Center, Utah State University, 84322-4705, Logan, UT, USA
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Abstract
Thermophilic fungi are a small assemblage in mycota that have a minimum temperature of growth at or above 20 degrees C and a maximum temperature of growth extending up to 60 to 62 degrees C. As the only representatives of eukaryotic organisms that can grow at temperatures above 45 degrees C, the thermophilic fungi are valuable experimental systems for investigations of mechanisms that allow growth at moderately high temperature yet limit their growth beyond 60 to 62 degrees C. Although widespread in terrestrial habitats, they have remained underexplored compared to thermophilic species of eubacteria and archaea. However, thermophilic fungi are potential sources of enzymes with scientific and commercial interests. This review, for the first time, compiles information on the physiology and enzymes of thermophilic fungi. Thermophilic fungi can be grown in minimal media with metabolic rates and growth yields comparable to those of mesophilic fungi. Studies of their growth kinetics, respiration, mixed-substrate utilization, nutrient uptake, and protein breakdown rate have provided some basic information not only on thermophilic fungi but also on filamentous fungi in general. Some species have the ability to grow at ambient temperatures if cultures are initiated with germinated spores or mycelial inoculum or if a nutritionally rich medium is used. Thermophilic fungi have a powerful ability to degrade polysaccharide constituents of biomass. The properties of their enzymes show differences not only among species but also among strains of the same species. Their extracellular enzymes display temperature optima for activity that are close to or above the optimum temperature for the growth of organism and, in general, are more heat stable than those of the mesophilic fungi. Some extracellular enzymes from thermophilic fungi are being produced commercially, and a few others have commercial prospects. Genes of thermophilic fungi encoding lipase, protease, xylanase, and cellulase have been cloned and overexpressed in heterologous fungi, and pure crystalline proteins have been obtained for elucidation of the mechanisms of their intrinsic thermostability and catalysis. By contrast, the thermal stability of the few intracellular enzymes that have been purified is comparable to or, in some cases, lower than that of enzymes from the mesophilic fungi. Although rigorous data are lacking, it appears that eukaryotic thermophily involves several mechanisms of stabilization of enzymes or optimization of their activity, with different mechanisms operating for different enzymes.
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Affiliation(s)
- R Maheshwari
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India.
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Henriksson G, Zhang L, Li J, Ljungquist P, Reitberger T, Pettersson G, Johansson G. Is cellobiose dehydrogenase from Phanerochaete chrysosporium a lignin degrading enzyme? BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1480:83-91. [PMID: 11004557 DOI: 10.1016/s0167-4838(00)00096-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Cellobiose dehydrogenase (CDH) is an extracellular redox enzyme of ping-pong type, i.e. it has separate oxidative and reductive half reactions. Several wood degrading fungi produce CDH, but the biological function of the enzyme is not known with certainty. It can, however, indirectly generate hydroxyl radicals by reducing Fe(3+) to Fe(2+) and O2 to H2O2. Hydroxyl radicals are then generated by a Fenton type reaction and they can react with various wood compounds, including lignin. In this work we study the effect of CDH on a non-phenolic lignin model compound (3,4-dimethoxyphenyl glycol). The results indicate that CDH can affect lignins in three important ways. (1) It breaks beta-ethers; (2) it demethoxylates aromatic structures in lignins; (3) it introduces hydroxyl groups in non-phenolic lignins. The gamma-irradiated model compound gave a similar pattern of products as the CDH treated model compound, when the samples were analyzed by HPLC, suggesting that hydroxyl radicals are the active component of the CDH system.
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Affiliation(s)
- G Henriksson
- Department of Pulp and Paper Technology and Chemistry, Royal Institute of Technology, Stockholm, Sweden.
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Li B, Rotsaert FA, Gold MH, Renganathan V. Homologous expression of recombinant cellobiose dehydrogenase in Phanerochaete chrysosporium. Biochem Biophys Res Commun 2000; 270:141-6. [PMID: 10733918 DOI: 10.1006/bbrc.2000.2381] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cellobiose dehydrogenase (CDH) is a novel extracellular hemoflavoenzyme from Phanerochaete chrysosporium and is produced only in cultures supplemented with cellulose. In this report, CDH from P. chrysosporium has been homologously expressed in cultures supplemented with glucose as the sole carbon source when no endogenous CDH is expressed. This was achieved by placing the cdh-1 gene under the control of the D-glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter (1.1 kb) fused upstream of the ATG start codon of cdh-1. The gpd promoter-chd-1 construct was inserted into the multiple cloning site of the expression vector pOGI18, which contained the Schizophyllum commune ade5 as a selectable marker. The P. chrysosporium ade1 auxotrophic strain OGC107-1 was transformed with the pAGC1 construct, and the prototrophic transformants were assayed for CDH activity. Approximately 50% of the Ade(+) transformants exhibited CDH activity in the extracellular medium of stationary cultures. At least one of the transformants produced high levels (500-600 U/liter) of recombinant CDH (rCDH). Purification by ammonium sulfate precipitation, Sephacryl S-200 chromatography, and FPLC using a Mono-Q 5/5 column yielded homogeneous rCDH. Physical, spectral, and kinetic characteristics of purified homologously expressed rCDH were similar to those of wild-type CDH. This expression system will enable site-directed mutagenesis studies to be carried out on CDH.
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Affiliation(s)
- B Li
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, 20000 N.W. Walker Road, Beaverton, Oregon 97006-8921, USA
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43
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Abstract
Cellobiose dehydrogenase (CDH) is an extracellular enzyme produced by various wood-degrading fungi. It oxidizes soluble cellodextrins, mannodextrins and lactose efficiently to their corresponding lactones by a ping-pong mechanism using a wide spectrum of electron acceptors including quinones, phenoxyradicals, Fe(3+), Cu(2+) and triiodide ion. Monosaccharides, maltose and molecular oxygen are poor substrates. CDH that adsorbs strongly and specifically to cellulose carries two prosthetic groups; namely, an FAD and a heme in two different domains that can be separated after limited proteolysis. The FAD-containing fragment carries all known catalytic and cellulose binding properties. One-electron acceptors, like ferricyanide, cytochrome c and phenoxy radicals, are, however, reduced more slowly by the FAD-fragment than by the intact enzyme, suggesting that the function of the heme group is to facilitate one-electron transfer. Non-heme forms of CDH have been found in the culture filtrate of some fungi (probably due to the action of fungal proteases) and were for a long time believed to represent a separate enzyme (cellobiose:quinone oxidoreductase, CBQ). The amino acid sequence of CDH has been determined and no significant homology with other proteins was detected for the heme domain. The FAD-domain sequence belongs to the GMC oxidoreductase family that includes, among others, Aspergillus niger glucose oxidase. The homology is most distinct in regions that correspond to the FAD-binding domain in glucose oxidase. A cellulose-binding domain of the fungal type is present in CDH from Myceliophtore thermophila (Sporotrichum thermophile), but in others an internal sequence rich in aromatic amino acid residues has been suggested to be responsible for the cellulose binding. The biological function of CDH is not fully understood, but recent results support a hydroxyl radical-generating mechanism whereby the radical can degrade and modify cellulose, hemicellulose and lignin. CDH has found technical use in highly selective amperometric biosensors and several other applications have been suggested.
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Affiliation(s)
- G Henriksson
- Department of Pulp and Paper Chemistry and Technology, Royal Institute of Technology, 100 44, Stockholm, Sweden.
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Hallberg BM, Bergfors T, Bäckbro K, Pettersson G, Henriksson G, Divne C. A new scaffold for binding haem in the cytochrome domain of the extracellular flavocytochrome cellobiose dehydrogenase. Structure 2000; 8:79-88. [PMID: 10673428 DOI: 10.1016/s0969-2126(00)00082-4] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The fungal oxidoreductase cellobiose dehydrogenase (CDH) degrades both lignin and cellulose, and is the only known extracellular flavocytochrome. This haemoflavoenzyme has a multidomain organisation with a b-type cytochrome domain linked to a large flavodehydrogenase domain. The two domains can be separated proteolytically to yield a functional cytochrome and a flavodehydrogenase. Here, we report the crystal structure of the cytochrome domain of CDH. RESULTS The crystal structure of the b-type cytochrome domain of CDH from the wood-degrading fungus Phanerochaete chrysosporium has been determined at 1.9 A resolution using multiple isomorphous replacement including anomalous scattering information. Three models of the cytochrome have been refined: the in vitro prepared cytochrome in its redox-inactive state (pH 7.5) and redox-active state (pH 4.6), as well as the naturally occurring cytochrome fragment. CONCLUSIONS The 190-residue long cytochrome domain of CDH folds as a beta sandwich with the topology of the antibody Fab V(H) domain. The haem iron is ligated by Met65 and His163, which confirms previous results from spectroscopic studies. This is only the second example of a b-type cytochrome with this ligation, the first being cytochrome b(562). The haem-propionate groups are surface exposed and, therefore, might play a role in the association between the cytochrome and flavoprotein domain, and in interdomain electron transfer. There are no large differences in overall structure of the cytochrome at redox-active pH as compared with the inactive form, which excludes the possibility that pH-dependent redox inactivation results from partial denaturation. From the electron-density map of the naturally occurring cytochrome, we conclude that it corresponds to the proteolytically prepared cytochrome domain.
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Affiliation(s)
- B M Hallberg
- Department of Cell and Molecular Biology, Structural Biology, Uppsala University, Uppsala, 751 24, Sweden
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Baminger U, Nidetzky B, Kulbe KD, Haltrich D. A simple assay for measuring cellobiose dehydrogenase activity in the presence of laccase. J Microbiol Methods 1999; 35:253-9. [PMID: 10333077 DOI: 10.1016/s0167-7012(99)00022-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The commonly used assay for measuring cellobiose dehydrogenase (CDH) activity, based on the reduction of dichlorophenol-indophenol (DCIP), has been adapted to measure this enzyme activity in the presence of laccase, which is often formed concurrently with CDH by a number of fungi. Laccase interferes with the assay by rapidly reoxidizing the reduced form of DCIP and can mask CDH activity completely. It can be conveniently and completely inhibited by 4 mM fluoride in the assay, while CDH activity is only slightly affected by the addition of this inhibitor. The modified assay enables the detection of low CDH activities even in the presence of very high excesses of laccase. It should be useful for screening culture supernatants of wood-degrading fungi for CDH since the assay is rapid and uses inexpensive and nontoxic reagents. Furthermore, it might be used for the detection of other enzyme activities which are assayed by following the reduction of quinones or analogue compounds such as DCIP.
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Affiliation(s)
- U Baminger
- Division of Biochemical Engineering, Institute of Food Technology, Universität für Bodenkultur BOKU (University of Agricultural Sciences Vienna), Wien, Austria
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Temp U, Eggert C. Novel interaction between laccase and cellobiose dehydrogenase during pigment synthesis in the white rot fungus Pycnoporus cinnabarinus. Appl Environ Microbiol 1999; 65:389-95. [PMID: 9925558 PMCID: PMC91037 DOI: 10.1128/aem.65.2.389-395.1999] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When glucose is the carbon source, the white rot fungus Pycnoporus cinnabarinus produces a characteristic red pigment, cinnabarinic acid, which is formed by laccase-catalyzed oxidation of the precursor 3-hydroxyanthranilic acid. When P. cinnabarinus was grown on media containing cellobiose or cellulose as the carbon source, the amount of cinnabarinic acid that accumulated was reduced or, in the case of cellulose, no cinnabarinic acid accumulated. Cellobiose-dependent quinone reducing enzymes, the cellobiose dehydrogenases (CDHs), inhibited the redox interaction between laccase and 3-hydroxyanthranilic acid. Two distinct proteins were purified from cellulose-grown cultures of P. cinnabarinus; these proteins were designated CDH I and CDH II. CDH I and CDH II were both monomeric proteins and had apparent molecular weights of about 81,000 and 101,000, respectively, as determined by both gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI values were approximately 5.9 for CDH I and 3.8 for CDH II. Both CDHs used several known CDH substrates as electron acceptors and specifically adsorbed to cellulose. Only CDH II could reduce cytochrome c. The optimum pH values for CDH I and CDH II were 5.5 and 4.5, respectively. In in vitro experiments, both enzymes inhibited laccase-mediated formation of cinnabarinic acid. Oxidation intermediates of 3-hydroxyanthranilic acid served as endogenous electron acceptors for the two CDHs from P. cinnabarinus. These results demonstrated that in the presence of a suitable cellulose-derived electron donor, CDHs can regenerate fungal metabolites oxidized by laccase, and they also supported the hypothesis that CDHs act as links between cellulolytic and ligninolytic pathways.
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Affiliation(s)
- U Temp
- Institute of General Microbiology and Microbial Genetics, Friedrich Schiller University Jena, 07743 Jena, Germany
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