1
|
de Araújo EA, Cortez AA, Pellegrini VDOA, Vacilotto MM, Cruz AF, Batista PR, Polikarpov I. Molecular mechanism of cellulose depolymerization by the two-domain BlCel9A enzyme from the glycoside hydrolase family 9. Carbohydr Polym 2024; 329:121739. [PMID: 38286536 DOI: 10.1016/j.carbpol.2023.121739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 12/20/2023] [Accepted: 12/23/2023] [Indexed: 01/31/2024]
Abstract
Carbohydrate-active enzymes from the glycoside hydrolase family 9 (GH9) play a key role in processing lignocellulosic biomass. Although the structural features of some GH9 enzymes are known, the molecular mechanisms that drive their interactions with cellulosic substrates remain unclear. To investigate the molecular mechanisms that the two-domain Bacillus licheniformis BlCel9A enzyme utilizes to depolymerize cellulosic substrates, we used a combination of biochemical assays, X-ray crystallography, small-angle X-ray scattering, and molecular dynamics simulations. The results reveal that BlCel9A breaks down cellulosic substrates, releasing cellobiose and glucose as the major products, but is highly inefficient in cleaving oligosaccharides shorter than cellotetraose. In addition, fungal lytic polysaccharide oxygenase (LPMO) TtLPMO9H enhances depolymerization of crystalline cellulose by BlCel9A, while exhibiting minimal impact on amorphous cellulose. The crystal structures of BlCel9A in both apo form and bound to cellotriose and cellohexaose were elucidated, unveiling the interactions of BlCel9A with the ligands and their contribution to substrate binding and products release. MD simulation analysis reveals that BlCel9A exhibits higher interdomain flexibility under acidic conditions, and SAXS experiments indicate that the enzyme flexibility is induced by pH and/or temperature. Our findings provide new insights into BlCel9A substrate specificity and binding, and synergy with the LPMOs.
Collapse
Affiliation(s)
- Evandro Ares de Araújo
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Giuseppe Maximo Scolfaro, 10000, Campinas, SP 13083-970, Brazil; Sao Carlos Institute of Physics, University of Sao Paulo, Av. Trabalhador Sao Carlense, 400, Sao Carlos, SP 13566-590, Brazil
| | - Anelyse Abreu Cortez
- Sao Carlos Institute of Physics, University of Sao Paulo, Av. Trabalhador Sao Carlense, 400, Sao Carlos, SP 13566-590, Brazil
| | | | - Milena Moreira Vacilotto
- Sao Carlos Institute of Physics, University of Sao Paulo, Av. Trabalhador Sao Carlense, 400, Sao Carlos, SP 13566-590, Brazil
| | - Amanda Freitas Cruz
- Sao Carlos Institute of Physics, University of Sao Paulo, Av. Trabalhador Sao Carlense, 400, Sao Carlos, SP 13566-590, Brazil
| | - Paulo Ricardo Batista
- Oswaldo Cruz Foundation, Scientific Computing Programme, Av. Brasil, 4365, Rio de Janeiro, RJ 21040-900, Brazil
| | - Igor Polikarpov
- Sao Carlos Institute of Physics, University of Sao Paulo, Av. Trabalhador Sao Carlense, 400, Sao Carlos, SP 13566-590, Brazil.
| |
Collapse
|
2
|
Sidar A, Albuquerque ED, Voshol GP, Ram AFJ, Vijgenboom E, Punt PJ. Carbohydrate Binding Modules: Diversity of Domain Architecture in Amylases and Cellulases From Filamentous Microorganisms. Front Bioeng Biotechnol 2020; 8:871. [PMID: 32850729 PMCID: PMC7410926 DOI: 10.3389/fbioe.2020.00871] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/07/2020] [Indexed: 12/11/2022] Open
Abstract
Enzymatic degradation of abundant renewable polysaccharides such as cellulose and starch is a field that has the attention of both the industrial and scientific community. Most of the polysaccharide degrading enzymes are classified into several glycoside hydrolase families. They are often organized in a modular manner which includes a catalytic domain connected to one or more carbohydrate-binding modules. The carbohydrate-binding modules (CBM) have been shown to increase the proximity of the enzyme to its substrate, especially for insoluble substrates. Therefore, these modules are considered to enhance enzymatic hydrolysis. These properties have played an important role in many biotechnological applications with the aim to improve the efficiency of polysaccharide degradation. The domain organization of glycoside hydrolases (GHs) equipped with one or more CBM does vary within organisms. This review comprehensively highlights the presence of CBM as ancillary modules and explores the diversity of GHs carrying one or more of these modules that actively act either on cellulose or starch. Special emphasis is given to the cellulase and amylase distribution within the filamentous microorganisms from the genera of Streptomyces and Aspergillus that are well known to have a great capacity for secreting a wide range of these polysaccharide degrading enzyme. The potential of the CBM and other ancillary domains for the design of improved polysaccharide decomposing enzymes is discussed.
Collapse
Affiliation(s)
- Andika Sidar
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands.,Department of Food Science and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Erica D Albuquerque
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands.,Sun Pharmaceutical Industries Europe BV., Hoofddorp, Netherlands
| | - Gerben P Voshol
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands.,Dutch DNA Biotech B.V., Utrecht, Netherlands
| | - Arthur F J Ram
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands
| | - Erik Vijgenboom
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands
| | - Peter J Punt
- Department of Microbial Biotechnology, Institute of Biology Leiden, Leiden, Netherlands.,Dutch DNA Biotech B.V., Utrecht, Netherlands
| |
Collapse
|
3
|
Huang HC, Qi LH, Chen YC, Tsai LC. Crystal structures of the GH6 Orpinomyces sp. Y102 CelC7 enzyme with exo and endo activity and its complex with cellobiose. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2019; 75:1138-1147. [PMID: 31793907 DOI: 10.1107/s2059798319013597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 10/04/2019] [Indexed: 11/10/2022]
Abstract
The catalytic domain (residues 128-449) of the Orpinomyces sp. Y102 CelC7 enzyme (Orp CelC7) exhibits cellobiohydrolase and cellotriohydrolase activities. Crystal structures of Orp CelC7 and its cellobiose-bound complex have been solved at resolutions of 1.80 and 2.78 Å, respectively. Cellobiose occupies subsites +1 and +2 within the active site of Orp CelC7 and forms hydrogen bonds to two key residues: Asp248 and Asp409. Furthermore, its substrate-binding sites have both tunnel-like and open-cleft conformations, suggesting that the glycoside hydrolase family 6 (GH6) Orp CelC7 enzyme may perform enzymatic hydrolysis in the same way as endoglucanases and cellobiohydrolases. LC-MS/MS analysis revealed cellobiose (major) and cellotriose (minor) to be the respective products of endo and exo activity of the GH6 Orp CelC7.
Collapse
Affiliation(s)
- Hsiao Chuan Huang
- Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei, Taiwan
| | - Liu Hong Qi
- Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei, Taiwan
| | - Yo Chia Chen
- Department of Biological Science and Technology, National Pingtung University of Science and Technology, Pingtung, Taiwan
| | - Li Chu Tsai
- Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei, Taiwan
| |
Collapse
|
4
|
Bao H, Zhang X, Su H, Li L, Lv Z, Zhang X. Study on the hydrogen production ability of high-efficiency bacteria and synergistic fermentation of maize straw by a combination of strains. RSC Adv 2019; 9:9030-9040. [PMID: 35517707 PMCID: PMC9062066 DOI: 10.1039/c9ra00165d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 03/05/2019] [Indexed: 11/21/2022] Open
Abstract
Based on the principle of reciprocal symbiosis and co-metabolism of mixed culture microorganisms, a group of high-efficiency maize straw-degrading hydrogen-producing complex bacteria X9 + B2 was developed by a strain matching optimization experiment. Systematic research and optimization experiments were carried out on the mechanism of the main controlling factors affecting the hydrogen production of the complex bacteria. The results showed that the optimum conditions for the acid blasting pre-treatment of maize straw as a substrate were as follows: when the inoculation amount was 6% and the inoculum ratio was 1 : 1, at which point, we needed to simultaneously inoculate, the initial pH was 6, the substrate concentration was 12 g L-1, and the culture time was 40 h. The complex bacteria adopted the variable temperature and speed regulation hydrogen production operational mode; after the initial temperature of 37 °C for 8 hours, the temperature was gradually increased to 40 °C for 3 hours. The initial shaker speed was 90 rpm for 20 hours, and the speed was gradually increased to 130 rpm. The maximum hydrogen production rate obtained by the complex bacteria under these conditions was 12.6 mmol g-1, which was 1.6 times that of the single strain X9 with a maximum hydrogen production rate of 5.7 mmol g-1. Through continuous subculturing and the 10th, 20th, 40th, 60th, 80th, 100th and 120th generation fermentation hydrogen production stability test analysis, no significant difference was observed between generations; the maximum difference was not more than 5%, indicating better functional properties and stability.
Collapse
Affiliation(s)
- Hongxu Bao
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248,Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of SciencesShenyang 110016China,State Key Laboratory of Urban Water Resources and Environments, Harbin Institute of TechnologyHarbin 150090China+86 451 86282195+86 451 86282195
| | - Xin Zhang
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248,Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of SciencesShenyang 110016China
| | - Hongzhi Su
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248
| | - Liangyu Li
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248
| | - Zhizhong Lv
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248
| | - Xinyue Zhang
- School of Environmental Science, Liaoning UniversityShenyang 110036China+86 024 62204818+86 024 62202248
| |
Collapse
|
5
|
Schiano-di-Cola C, Røjel N, Jensen K, Kari J, Sørensen TH, Borch K, Westh P. Systematic deletions in the cellobiohydrolase (CBH) Cel7A from the fungus Trichoderma reesei reveal flexible loops critical for CBH activity. J Biol Chem 2018; 294:1807-1815. [PMID: 30538133 DOI: 10.1074/jbc.ra118.006699] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 12/08/2018] [Indexed: 11/06/2022] Open
Abstract
Glycoside hydrolase family 7 (GH7) cellulases are some of the most efficient degraders of cellulose, making them particularly relevant for industries seeking to produce renewable fuels from lignocellulosic biomass. The secretome of the cellulolytic model fungus Trichoderma reesei contains two GH7s, termed TrCel7A and TrCel7B. Despite having high structural and sequence similarities, the two enzymes are functionally quite different. TrCel7A is an exolytic, processive cellobiohydrolase (CBH), with high activity on crystalline cellulose, whereas TrCel7B is an endoglucanase (EG) with a preference for more amorphous cellulose. At the structural level, these functional differences are usually ascribed to the flexible loops that cover the substrate-binding areas. TrCel7A has an extensive tunnel created by eight peripheral loops, and the absence of four of these loops in TrCel7B makes its catalytic domain a more open cleft. To investigate the structure-function relationships of these loops, here we produced and kinetically characterized several variants in which four loops unique to TrCel7A were individually deleted to resemble the arrangement in the TrCel7B structure. Analysis of a range of kinetic parameters consistently indicated that the B2 loop, covering the substrate-binding subsites -3 and -4 in TrCel7A, was a key determinant for the difference in CBH- or EG-like behavior between TrCel7A and TrCel7B. Conversely, the B3 and B4 loops, located closer to the catalytic site in TrCel7A, were less important for these activities. We surmise that these results could be useful both in further mechanistic investigations and for guiding engineering efforts of this industrially important enzyme family.
Collapse
Affiliation(s)
- Corinna Schiano-di-Cola
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Nanna Røjel
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Kenneth Jensen
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark, and
| | - Jeppe Kari
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Trine Holst Sørensen
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark, and
| | - Peter Westh
- the Department of Biotechnology and Biomedicine, Technical University of Denmark, Building 224, DK-2800 Kgs. Lyngby, Denmark
| |
Collapse
|
6
|
Discovery and characterization of a thermostable two-domain GH6 endoglucanase from a compost metagenome. PLoS One 2018; 13:e0197862. [PMID: 29795644 PMCID: PMC5968413 DOI: 10.1371/journal.pone.0197862] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 05/09/2018] [Indexed: 11/19/2022] Open
Abstract
Enzymatic depolymerization of recalcitrant polysaccharides plays a key role in accessing the renewable energy stored within lignocellulosic biomass, and natural biodiversities may be explored to discover microbial enzymes that have evolved to conquer this task in various environments. Here, a metagenome from a thermophilic microbial community was mined to yield a novel, thermostable cellulase, named mgCel6A, with activity on an industrial cellulosic substrate (sulfite-pulped Norway spruce) and a glucomannanase side activity. The enzyme consists of a glycoside hydrolase family 6 catalytic domain (GH6) and a family 2 carbohydrate binding module (CBM2) that are connected by a linker rich in prolines and threonines. MgCel6A exhibited maximum activity at 85°C and pH 5.0 on carboxymethyl cellulose (CMC), but in prolonged incubations with the industrial substrate, the highest yields were obtained at 60°C, pH 6.0. Differential scanning calorimetry (DSC) indicated a Tm(app) of 76°C. Both functional data and the crystal structure, solved at 1.88 Å resolution, indicate that mgCel6A is an endoglucanase. Comparative studies with a truncated variant of the enzyme showed that the CBM increases substrate binding, while not affecting thermal stability. Importantly, at higher substrate concentrations the full-length enzyme was outperformed by the catalytic domain alone, underpinning previous suggestions that CBMs may be less useful in high-consistency bioprocessing.
Collapse
|
7
|
Zhang KD, Li W, Wang YF, Zheng YL, Tan FC, Ma XQ, Yao LS, Bayer EA, Wang LS, Li FL. Processive Degradation of Crystalline Cellulose by a Multimodular Endoglucanase via a Wirewalking Mode. Biomacromolecules 2018; 19:1686-1696. [DOI: 10.1021/acs.biomac.8b00340] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kun-Di Zhang
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, People’s Republic of China
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, People’s Republic of China
| | - Wen Li
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, People’s Republic of China
| | - Ye-Fei Wang
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, People’s Republic of China
| | - Yan-Lin Zheng
- College of Mathematics and Systems Science, Shandong University of Science and Technology, Qingdao, 266590, People’s Republic of China
| | - Fang-Cheng Tan
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, People’s Republic of China
| | - Xiao-Qing Ma
- Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, 266101, People’s Republic of China
| | - Li-Shan Yao
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, People’s Republic of China
| | - Edward A. Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Lu-Shan Wang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, People’s Republic of China
| | - Fu-Li Li
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, People’s Republic of China
| |
Collapse
|
8
|
Zheng F, Tu T, Wang X, Wang Y, Ma R, Su X, Xie X, Yao B, Luo H. Enhancing the catalytic activity of a novel GH5 cellulase GtCel5 from Gloeophyllum trabeum CBS 900.73 by site-directed mutagenesis on loop 6. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:76. [PMID: 29588661 PMCID: PMC5863444 DOI: 10.1186/s13068-018-1080-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 03/14/2018] [Indexed: 05/17/2023]
Abstract
BACKGROUND Cellulases of glycosyl hydrolase (GH) family 5 share a (β/α)8 TIM-barrel fold structure with eight βα loops surrounding the catalytic pocket. These loops exposed on the surface play a vital role in protein functions, primarily due to the interactions of some key amino acids with solvent and ligand molecules. It has been reported that motions of these loops facilitate substrate access and product release, and loops 6 and 7 located at the substrate entrance of the binding pocket promote proton transfer reaction at the catalytic site motions. However, the role of these flexible loops in catalysis of GH5 cellulase remains to be explored. RESULTS In the present study, an acidic, mesophilic GH5 cellulase (with optimal activity at pH 4.0 and 70 °C), GtCel5, was identified in Gloeophyllum trabeum CBS 900.73. The specific activities of GtCel5 toward CMC-Na, barley β-glucan, and lichenan were 1117 ± 43, 6257 ± 26 and 5318 ± 54 U/mg, respectively. Multiple sequence alignment indicates that one amino acid residue at position 233 on the loop 6 shows semi-conservativeness and might contribute to the great catalytic performance. Saturation mutagenesis at position 233 was then conducted to reveal the vital roles of this position in enzyme properties. In comparison to the wild type, variants N233A and N233G showed decreased optimal temperature (- 10 °C) but increased activities (27 and 70%) and catalytic efficiencies (kcat/Km; 45 and 52%), respectively. The similar roles of position 233 in catalytic performance were also verified in the other two GH5 homologs, TeEgl5A and PoCel5, by reverse mutation. Further molecular dynamics simulations suggested that the substitution of asparagine with alanine or glycine may introduce more hydrogen bonds, increase the flexibility of loop 6, enhance the interactions between enzyme and substrate, and thus improve the substrate affinity and catalytic efficiency. CONCLUSION This study proposed a novel cellulase with potentials for industrial application. A specific position was identified to play key roles in cellulase-substrate interactions and enzyme catalysis. It is of great importance for understanding the binding mechanism of GH5 cellulases, and provides an effective strategy to improve the catalytic performance of cellulases.
Collapse
Affiliation(s)
- Fei Zheng
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, 100083 People’s Republic of China
| | - Tao Tu
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| | - Xiaoyu Wang
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, 100083 People’s Republic of China
| | - Yuan Wang
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| | - Rui Ma
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| | - Xiaoyun Su
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| | - Xiangming Xie
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, 100083 People’s Republic of China
| | - Bin Yao
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| | - Huiying Luo
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian, Beijing, 100081 People’s Republic of China
| |
Collapse
|
9
|
Zhang Z, Wang M, Gao R, Yu X, Chen G. Synergistic effect of thermostable β-glucosidase TN0602 and cellulase on cellulose hydrolysis. 3 Biotech 2017; 7:54. [PMID: 28444598 DOI: 10.1007/s13205-017-0672-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 02/27/2017] [Indexed: 01/22/2023] Open
Abstract
Thermophilic enzymes have many potential benefits in industrial production with increased flexibility related to process configurations. A thermostable β-glucosidase from Thermotoga naphthophila RUK-10 was found to possess catalytic activity for cellobiose hydrolysis with a high potential for application in biomass conversion. The aggregation of cellobiose often has an inhibitory effect on cellobiohydrolases and endoglucanases during cellulose hydrolysis. The presence of β-glucosidases has a significant effect on reducing inhibition from hydrolytic products by hydrolysing the intermedia cellobiose. In this study, β-glucosidase TN0602 exhibited a high tolerance to glucose and high thermostability even after a long incubation (>72 h). Additionally, supplementing β-glucosidase TN0602 with microcrystalline cellulose, untreated corn straw and steam-exploded corn straw hydrolysis reactions containing a commercial cellulase led to an increased conversion rate in released glucose compared to hydrolysis without the addition of β-glucosidase (15.82, 30.62 and 35.21%, respectively); the increase of conversion rates were 61.86, 93.50 and 94.55%. It was thus shown that an obvious synergistic effect exists between TN0602 and cellulases for cellulose hydrolysis, suggesting its potential as a component of enzymatic cocktails for the conversion of lignocellulosic biomass to other chemicals.
Collapse
|
10
|
Expression and Characteristics of an Endoglucanase from Trichoderma atroviride (TaEGII) in Saccharomyces cerevisiae. Appl Biochem Biotechnol 2017; 182:1158-1170. [DOI: 10.1007/s12010-016-2389-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 12/28/2016] [Indexed: 01/27/2023]
|
11
|
Sørensen TH, Windahl MS, McBrayer B, Kari J, Olsen JP, Borch K, Westh P. Loop variants of the thermophileRasamsonia emersoniiCel7A with improved activity against cellulose. Biotechnol Bioeng 2016; 114:53-62. [DOI: 10.1002/bit.26050] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 07/08/2016] [Accepted: 07/11/2016] [Indexed: 01/09/2023]
Affiliation(s)
- Trine Holst Sørensen
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | | | | | - Jeppe Kari
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | - Johan Pelck Olsen
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | | | - Peter Westh
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| |
Collapse
|
12
|
Verma PK, Bhardwaj NK, Singh SP. Improving the material efficiency of recycled furnish for papermaking through enzyme modifications. CAN J CHEM ENG 2016. [DOI: 10.1002/cjce.22410] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Piyush Kumar Verma
- Department of Paper Technology, Indian Institute of Technology Roorkee; Saharanpur Campus; Saharanpur 247001 India
| | - Nishi Kant Bhardwaj
- Avantha Centre for Industrial Research & Development; Yamuna Nagar 135 001 India
| | - Surendra Pal Singh
- Department of Paper Technology, Indian Institute of Technology Roorkee; Saharanpur Campus; Saharanpur 247001 India
| |
Collapse
|
13
|
Mori M, Ichikawa M, Kiguchi Y, Miyazaki T, Hattori M, Nishikawa A, Tonozuka T. A Surface Loop in the N-Terminal Domain of <i>Pedobacter heparinus </i>Heparin Lyase II is Important for Activity. J Appl Glycosci (1999) 2016; 63:7-11. [PMID: 34354475 PMCID: PMC8056909 DOI: 10.5458/jag.jag.jag-2015_019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/15/2015] [Indexed: 12/02/2022] Open
Abstract
Pedobacter heparinus heparin lyase II (PhHepII) is composed of N-terminal, central, and C-terminal domains. A long surface loop, designated loop-A, is in the N-terminal domain and is composed of amino acids 84-89. In this study, we deleted two, three, or four residues in loop-A to create Δ86-87, Δ85-87, and Δ84-87 PhHepII deletion mutants. We hypothesized that the deletions would increase PhHepII thermostability. After heating purified PhHepII enzymes at 45 °C for 5 min, 6.1 % of the enzyme activity remained in wild-type PhHepII, whereas 10.6 % of the enzyme activity remained in Δ86-87 PhHepII. The results indicated that the deletion caused a significant decrease in the activity, although Δ86-87 PhHepII is slightly more thermostable than wild-type PhHepII. In addtion, Δ85-87 and Δ84-87 PhHepII had weak or no enzyme activity, even when unheated. Circular dichroism spectra showed that Δ85-87 PhHepII was properly folded. These results suggest that the flexibility of loop-A is important for PhHepII enzyme activity.
Collapse
Affiliation(s)
- Marina Mori
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Megumi Ichikawa
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Yumiko Kiguchi
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Takatsugu Miyazaki
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Makoto Hattori
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Atsushi Nishikawa
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| | - Takashi Tonozuka
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology
| |
Collapse
|
14
|
Xu X, Li J, Zhang W, Huang H, Shi P, Luo H, Liu B, Zhang Y, Zhang Z, Fan Y, Yao B. A Neutral Thermostable β-1,4-Glucanase from Humicola insolens Y1 with Potential for Applications in Various Industries. PLoS One 2015; 10:e0124925. [PMID: 25909505 PMCID: PMC4409357 DOI: 10.1371/journal.pone.0124925] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 03/10/2015] [Indexed: 01/26/2023] Open
Abstract
We cloned a new glycoside hydrolase family 6 gene, Hicel6C, from the thermophilic fungus Humicola insolens Y1 and expressed it in Pichia pastoris. Using barley β-glucan as a substrate, recombinant HiCel6C protein exhibited neutral pH (6.5) and high temperature (70°C) optima. Distinct from most reported acidic fungal endo-β-1,4-glucanases, HiCel6C was alkali-tolerant, retaining greater than 98.0, 61.2, and 27.6% of peak activity at pH 8.0, 9.0, and 10.0, respectively, and exhibited good stability over a wide pH range (pH 5.0−11.0) and at temperatures up to 60°C. The Km and Vmax values of HiCel6C for barley β-glucan were 1.29 mg/mL and 752 μmol/min·mg, respectively. HiCel6C was strictly specific for the β-1,4-glucoside linkage exhibiting activity toward barley β-glucan, lichenan, and carboxy methylcellulose sodium salt (CMC-Na), but not toward laminarin (1,3-β-glucan). HiCel6C cleaved the internal glycosidic linkages of cellooligosaccharides randomly and thus represents an endo-cleaving enzyme. The predominant product of polysaccharide hydrolysis by HiCel6C was cellobiose, suggesting that it functions by an endo-processive mechanism. The favorable properties of HiCel6C make it a good candidate for basic research and for applications in the textile and brewing industries.
Collapse
Affiliation(s)
- Xinxin Xu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jinyang Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Wei Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
- * E-mail: (WZ); (BY)
| | - Huoqing Huang
- Key Laboratory of Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Pengjun Shi
- Key Laboratory of Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Huiying Luo
- Key Laboratory of Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Bo Liu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yuhong Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Zhifang Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yunliu Fan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Bin Yao
- Key Laboratory of Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
- * E-mail: (WZ); (BY)
| |
Collapse
|
15
|
Wu G, Sun J, Yu S, Dong Q, Zhuang G, Liu W, Lin J, Qu Y. Improved activity of the Cel5A endoglucanase in Saccharomyces cerevisiae deletion mutants defective in oxidative stress defense mechanisms. Biotechnol Lett 2015; 37:1081-9. [PMID: 25650342 DOI: 10.1007/s10529-015-1771-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Accepted: 01/20/2015] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Developing a Saccharomyces cerevisiae system for optimizing the expression of recombinant eukaryotic proteins. RESULTS Two deletion mutants, which were hypersensitive to H2O2, were obtained by knocking out CTT1 and SOD2, respectively. The mutation rate of the mutants was up to over 4000 times of the spontaneous mutation rate when treated with H2O2. Endoglucanase Cel5A was used as a model enzyme to evaluate the system for improving the expression of the recombinant protein. Sixteen mutants of the RDKY3615 (ctt1∆) transformant and seven mutants of the RDKY3615 (sod2∆) transformant had significantly high Cel5A activity, while none mutants of the RDKY3615 transformant had significantly high enzyme activity. CONCLUSION The combination of deletion mutagenesis and H2O2 treatment greatly accelerate the generation of genetic variants and will be a useful tool in improving the heterologous expression in S. cerevisiae.
Collapse
Affiliation(s)
- Guochao Wu
- Research Center for Eco-Environmental Science, Chinese Academy of Science, Beijing, People's Republic of China
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Payne CM, Knott BC, Mayes HB, Hansson H, Himmel ME, Sandgren M, Ståhlberg J, Beckham GT. Fungal Cellulases. Chem Rev 2015; 115:1308-448. [DOI: 10.1021/cr500351c] [Citation(s) in RCA: 533] [Impact Index Per Article: 59.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Christina M. Payne
- Department
of Chemical and Materials Engineering and Center for Computational
Sciences, University of Kentucky, 177 F. Paul Anderson Tower, Lexington, Kentucky 40506, United States
| | - Brandon C. Knott
- National
Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver
West Parkway, Golden, Colorado 80401, United States
| | - Heather B. Mayes
- Department
of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Henrik Hansson
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Michael E. Himmel
- Biosciences
Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Mats Sandgren
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Jerry Ståhlberg
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Gregg T. Beckham
- National
Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver
West Parkway, Golden, Colorado 80401, United States
| |
Collapse
|
17
|
Qin Y, Qu Y. Asn124 of Cel5A from Hypocrea jecorina not only provides the N-glycosylation site but is also essential in maintaining enzymatic activity. BMB Rep 2014; 47:256-61. [PMID: 24286316 PMCID: PMC4163860 DOI: 10.5483/bmbrep.2014.47.5.166] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Indexed: 11/24/2022] Open
Abstract
To investigate the function of N-glycosylation of Cel5A (endoglucanase II) from Hypocrea jecorina, two N-glycosylation site deletion Cel5A mutants (rN124D and rN124H) were expressed in Saccharomyces cerevisiae. The weights of these recombinant mutants were 54 kDa, which were lower than that of rCel5A. This result was expected to be attributed to deglycosylation. The enzyme activity of rN124H was greatly reduced to 60.6% compared with rCel5A, whereas rN124D showed slightly lower activity (10%) than that of rCel5A. rN124D and rN124H showed different thermal stabilities compared with the glycosylated rCel5A, especially at lower pH value. Thermal stabilities were reduced and improved for rN124D and rN124H, respectively. Circular dichroism spectroscopy showed that the modification of secondary structure by mutation may be the reason for the change in enzymatic activity and thermal stability. [BMB Reports 2014; 47(5): 256-261]
Collapse
Affiliation(s)
- Yuqi Qin
- National Glycoengineering Research Center, and State Key Laboratory of Microbial Technology, Shandong University, 27, Shanda South Road, Jinan, Shandong 250100, China
| | - Yinbo Qu
- National Glycoengineering Research Center, and State Key Laboratory of Microbial Technology, Shandong University, 27, Shanda South Road, Jinan, Shandong 250100, China
| |
Collapse
|
18
|
Granum DM, Schutt TC, Maupin CM. Computational Evaluation of the Dynamic Fluctuations of Peripheral Loops Enclosing the Catalytic Tunnel of a Family 7 Cellobiohydrolase. J Phys Chem B 2014; 118:5340-9. [DOI: 10.1021/jp5011555] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David M. Granum
- Chemical
and Biological Engineering
Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Timothy C. Schutt
- Chemical
and Biological Engineering
Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - C. Mark Maupin
- Chemical
and Biological Engineering
Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| |
Collapse
|
19
|
Zhang C, Wang Y, Li Z, Zhou X, Zhang W, Zhao Y, Lu X. Characterization of a multi-function processive endoglucanase CHU_2103 from Cytophaga hutchinsonii. Appl Microbiol Biotechnol 2014; 98:6679-87. [DOI: 10.1007/s00253-014-5640-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Revised: 02/20/2014] [Accepted: 02/23/2014] [Indexed: 11/28/2022]
|
20
|
Granum DM, Vyas S, Sambasivarao SV, Maupin CM. Computational Evaluations of Charge Coupling and Hydrogen Bonding in the Active Site of a Family 7 Cellobiohydrolase. J Phys Chem B 2014; 118:434-48. [DOI: 10.1021/jp408536s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David M. Granum
- Chemical and Biological Engineering Department and ‡Chemistry and Geochemistry Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Shubham Vyas
- Chemical and Biological Engineering Department and ‡Chemistry and Geochemistry Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Somisetti V. Sambasivarao
- Chemical and Biological Engineering Department and ‡Chemistry and Geochemistry Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - C. Mark Maupin
- Chemical and Biological Engineering Department and ‡Chemistry and Geochemistry Department, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| |
Collapse
|
21
|
V. Sambasivarao S, M. Granum D, Wang H, Mark Maupin C. Identifying the Enzymatic Mode of Action for Cellulase Enzymes by Means of Docking Calculations and a Machine Learning Algorithm. AIMS MOLECULAR SCIENCE 2014. [DOI: 10.3934/molsci.2014.1.59] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
|
22
|
Wu M, Bu L, Vuong TV, Wilson DB, Crowley MF, Sandgren M, Ståhlberg J, Beckham GT, Hansson H. Loop motions important to product expulsion in the Thermobifida fusca glycoside hydrolase family 6 cellobiohydrolase from structural and computational studies. J Biol Chem 2013; 288:33107-17. [PMID: 24085303 DOI: 10.1074/jbc.m113.502765] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellobiohydrolases (CBHs) are typically major components of natural enzyme cocktails for biomass degradation. Their active sites are enclosed in a tunnel, enabling processive hydrolysis of cellulose chains. Glycoside hydrolase Family 6 (GH6) CBHs act from nonreducing ends by an inverting mechanism and are present in many cellulolytic fungi and bacteria. The bacterial Thermobifida fusca Cel6B (TfuCel6B) exhibits a longer and more enclosed active site tunnel than its fungal counterparts. Here, we determine the structures of two TfuCel6B mutants co-crystallized with cellobiose, D274A (catalytic acid), and the double mutant D226A/S232A, which targets the putative catalytic base and a conserved serine that binds the nucleophilic water. The ligand binding and the structure of the active site are retained when compared with the wild type structure, supporting the hypothesis that these residues are directly involved in catalysis. One structure exhibits crystallographic waters that enable construction of a model of the α-anomer product after hydrolysis. Interestingly, the product sites of TfuCel6B are completely enclosed by an "exit loop" not present in fungal GH6 CBHs and by an extended "bottom loop". From the structures, we hypothesize that either of the loops enclosing the product subsites in the TfuCel6B active site tunnel must open substantially for product release. With simulation, we demonstrate that both loops can readily open to allow product release with equal probability in solution or when the enzyme is engaged on cellulose. Overall, this study reveals new structural details of GH6 CBHs likely important for functional differences among enzymes from this important family.
Collapse
Affiliation(s)
- Miao Wu
- From the Department of Molecular Biology, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Wu I, Heel T, Arnold FH. Role of cysteine residues in thermal inactivation of fungal Cel6A cellobiohydrolases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1539-44. [PMID: 23676789 DOI: 10.1016/j.bbapap.2013.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 05/01/2013] [Accepted: 05/06/2013] [Indexed: 10/26/2022]
Abstract
Numerous protein engineering studies have focused on increasing the thermostability of fungal cellulases to improve production of fuels and chemicals from lignocellulosic feedstocks. However, the engineered enzymes still undergo thermal inactivation at temperatures well below the inactivation temperatures of hyperthermophilic cellulases. In this report, we investigated the role of free cysteines in the thermal inactivation of wild-type and engineered fungal family 6 cellobiohydrolases (Cel6A). The mechanism of thermal inactivation of Cel6A is consistent with disulfide bond degradation and thiol-disulfide exchange. Circular dichroism spectroscopy revealed that a thermostable variant lacking free cysteines refolds to a native-like structure and retains activity after heat treatment over the pH range 5-9. Whereas conserved disulfide bonds are essential for retaining activity after heat treatment, free cysteines contribute to irreversible thermal inactivation in engineered thermostable Cel6A as well as Cel6A from Hypocrea jecorina and Humicola insolens.
Collapse
Affiliation(s)
- Indira Wu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | | | | |
Collapse
|
24
|
Taylor CB, Payne CM, Himmel ME, Crowley MF, McCabe C, Beckham GT. Binding Site Dynamics and Aromatic–Carbohydrate Interactions in Processive and Non-Processive Family 7 Glycoside Hydrolases. J Phys Chem B 2013; 117:4924-33. [DOI: 10.1021/jp401410h] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Courtney B. Taylor
- Department
of Chemical and Biomolecular
Engineering, Vanderbilt University, Nashville,
Tennessee 37235, United States
| | - Christina M. Payne
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
80401, United States
- Department
of Chemical and Materials
Engineering, University of Kentucky, Lexington,
Kentucky 40506, United States
| | - Michael E. Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
80401, United States
| | - Michael F. Crowley
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
80401, United States
| | - Clare McCabe
- Department
of Chemical and Biomolecular
Engineering, Vanderbilt University, Nashville,
Tennessee 37235, United States
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235,
United States
| | - Gregg T. Beckham
- National
Bioenergy Center, National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, United
States
| |
Collapse
|
25
|
Payne CM, Baban J, Horn SJ, Backe PH, Arvai AS, Dalhus B, Bjørås M, Eijsink VGH, Sørlie M, Beckham GT, Vaaje-Kolstad G. Hallmarks of processivity in glycoside hydrolases from crystallographic and computational studies of the Serratia marcescens chitinases. J Biol Chem 2012; 287:36322-30. [PMID: 22952223 DOI: 10.1074/jbc.m112.402149] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Degradation of recalcitrant polysaccharides in nature is typically accomplished by mixtures of processive and nonprocessive glycoside hydrolases (GHs), which exhibit synergistic activity wherein nonprocessive enzymes provide new sites for productive attachment of processive enzymes. GH processivity is typically attributed to active site geometry, but previous work has demonstrated that processivity can be tuned by point mutations or removal of single loops. To gain additional insights into the differences between processive and nonprocessive enzymes that give rise to their synergistic activities, this study reports the crystal structure of the catalytic domain of the GH family 18 nonprocessive endochitinase, ChiC, from Serratia marcescens. This completes the structural characterization of the co-evolved chitinolytic enzymes from this bacterium and enables structural analysis of their complementary functions. The ChiC catalytic module reveals a shallow substrate-binding cleft that lacks aromatic residues vital for processivity, a calcium-binding site not previously seen in GH18 chitinases, and, importantly, a displaced catalytic acid (Glu-141), suggesting flexibility in the catalytic center. Molecular dynamics simulations of two processive chitinases (ChiA and ChiB), the ChiC catalytic module, and an endochitinase from Lactococcus lactis show that the nonprocessive enzymes have more flexible catalytic machineries and that their bound ligands are more solvated and flexible. These three features, which relate to the more dynamic on-off ligand binding processes associated with nonprocessive action, correlate to experimentally measured differences in processivity of the S. marcescens chitinases. These newly defined hallmarks thus appear to be key dynamic metrics in determining processivity in GH enzymes complementing structural insights.
Collapse
Affiliation(s)
- Christina M Payne
- Biosciences Center, National Renewable Energy Laboratory, Golden Colorado 80401, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Chen HL, Chen YC, Lu MYJ, Chang JJ, Wang HTC, Ke HM, Wang TY, Ruan SK, Wang TY, Hung KY, Cho HY, Lin WT, Shih MC, Li WH. A highly efficient β-glucosidase from the buffalo rumen fungus Neocallimastix patriciarum W5. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:24. [PMID: 22515264 PMCID: PMC3403894 DOI: 10.1186/1754-6834-5-24] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 04/19/2012] [Indexed: 05/07/2023]
Abstract
BACKGROUND Cellulose, which is the most abundant renewable biomass on earth, is a potential bio-resource of alternative energy. The hydrolysis of plant polysaccharides is catalyzed by microbial cellulases, including endo-β-1,4-glucanases, cellobiohydrolases, cellodextrinases, and β-glucosidases. Converting cellobiose by β-glucosidases is the key factor for reducing cellobiose inhibition and enhancing the efficiency of cellulolytic enzymes for cellulosic ethanol production. RESULTS In this study, a cDNA encoding β-glucosidase was isolated from the buffalo rumen fungus Neocallimastix patriciarum W5 and is named NpaBGS. It has a length of 2,331 bp with an open reading frame coding for a protein of 776 amino acid residues, corresponding to a theoretical molecular mass of 85.1 kDa and isoelectric point of 4.4. Two GH3 catalytic domains were found at the N and C terminals of NpaBGS by sequence analysis. The cDNA was expressed in Pichia pastoris and after protein purification, the enzyme displayed a specific activity of 34.5 U/mg against cellobiose as the substrate. Enzymatic assays showed that NpaBGS was active on short cello-oligosaccharides from various substrates. A weak activity in carboxymethyl cellulose (CMC) digestion indicated that the enzyme might also have the function of an endoglucanase. The optimal activity was detected at 40°C and pH 5 ~ 6, showing that the enzyme prefers a weak acid condition. Moreover, its activity could be enhanced at 50°C by adding Mg2+ or Mn2+ ions. Interestingly, in simultaneous saccharification and fermentation (SSF) experiments using Saccharomyces cerevisiae BY4741 or Kluyveromyces marxianus KY3 as the fermentation yeast, NpaBGS showed advantages in cell growth, glucose production, and ethanol production over the commercial enzyme Novo 188. Moreover, we showed that the KY3 strain engineered with the NpaNGS gene can utilize 2 % dry napiergrass as the sole carbon source to produce 3.32 mg/ml ethanol when Celluclast 1.5 L was added to the SSF system. CONCLUSION Our characterizations of the novel β-glucosidase NpaBGS revealed that it has a preference of weak acidity for optimal yeast fermentation and an optimal temperature of ~40°C. Since NpaBGS performs better than Novo 188 under the living conditions of fermentation yeasts, it has the potential to be a suitable enzyme for SSF.
Collapse
Affiliation(s)
- Hsin-Liang Chen
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Yo-Chia Chen
- Department of Biological Science & Technology, National Pingtung University of Science & Technology, Neipu Hsiang, Pingtung, 91201, Taiwan
| | - Mei-Yeh Jade Lu
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Jui-Jen Chang
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
| | | | - Huei-Mien Ke
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
- Program in Microbial Genomics, National Chung-Hsing University, Taichung, 402, Taiwan
| | - Tzi-Yuan Wang
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Sz-Kai Ruan
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Tao-Yuan Wang
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Kuo-Yen Hung
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Hsing-Yi Cho
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung-Hsing University – Academia Sinica, Taipei, 115, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, 402, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Wan-Ting Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Ming-Che Shih
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung-Hsing University – Academia Sinica, Taipei, 115, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
- Biotechnology Center, National Chung-Hsing University, Taichung, 402, Taiwan
| | - Wen-Hsiung Li
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
- Biotechnology Center, National Chung-Hsing University, Taichung, 402, Taiwan
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, 60637, USA
| |
Collapse
|
27
|
Tamura M, Miyazaki T, Tanaka Y, Yoshida M, Nishikawa A, Tonozuka T. Comparison of the structural changes in two cellobiohydrolases, CcCel6A and CcCel6C, from Coprinopsis cinerea--a tweezer-like motion in the structure of CcCel6C. FEBS J 2012; 279:1871-82. [PMID: 22429290 DOI: 10.1111/j.1742-4658.2012.08568.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The basidiomycete Coprinopsis cinerea produces five cellobiohydrolases belonging to glycoside hydrolase family 6 (GH6). Among these enzymes, C. cinerea cellulase 6C (CcCel6C), but not C. cinerea cellulase 6A (CcCel6A), can efficiently hydrolyze carboxymethyl cellulose and is constitutively expressed in C. cinerea. In contrast, CcCel6A possesses a cellulose-binding domain, and is strongly induced by cellobiose. Here, we determined the crystal structures of the CcCel6A catalytic domain complexed with a Hepes buffer molecule, with cellobiose, and with p-nitrophenyl β-D-cellotrioside (pNPG3). A notable feature of the GH6 cellobiohydrolases is that the active site is enclosed by two loops to form a tunnel, and the loops have been demonstrated to open and close in response to ligand binding. The enclosed tunnel of CcCel6A-Hepes is seen as the open form, whereas the tunnels of CcCel6A-cellobiose and CcCel6A-pNPG3 adopt the closed form. pNPG3 was not hydrolyzed by CcCel6A, and bound in subsites +1 to +4. On the basis of this observation, we constructed two mutants, CcCel6A D164A and CcCel6C D102A. Neither CcCel6A D164A nor CcCel6C D102A hydrolyze phosphoric acid-swollen cellulose. We have previously determined the crystal structures of CcCel6C unbound and in complex with ligand, both of which adopt the open form. In the present study, both CcCel6A and CcCel6C mutants were identified as the closed form. However, the motion angle of CcCel6C was more than 10-fold greater than that of CcCel6A. The width of the active site cleft of CcCel6C was narrowed, owing to a tweezer-like motion.
Collapse
Affiliation(s)
- Mizuki Tamura
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | | | | | | | | | | |
Collapse
|
28
|
Marana SR. Structural and mechanistic fundamentals for designing of cellulases. Comput Struct Biotechnol J 2012; 2:e201209006. [PMID: 24688647 PMCID: PMC3962180 DOI: 10.5936/csbj.201209006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 09/20/2012] [Accepted: 09/23/2012] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sandro R Marana
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, São Paulo, 05513-970, SP, Brazil
| |
Collapse
|
29
|
Fox JM, Levine SE, Clark DS, Blanch HW. Initial- and Processive-Cut Products Reveal Cellobiohydrolase Rate Limitations and the Role of Companion Enzymes. Biochemistry 2011; 51:442-52. [DOI: 10.1021/bi2011543] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jerome M. Fox
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Seth E. Levine
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Douglas S. Clark
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Harvey W. Blanch
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| |
Collapse
|
30
|
Egusa S, Kitaoka T, Igarashi K, Samejima M, Goto M, Wariishi H. Preparation and enzymatic behavior of surfactant-enveloped enzymes for glycosynthesis in nonaqueous aprotic media. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.molcatb.2010.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
31
|
Lantz SE, Goedegebuur F, Hommes R, Kaper T, Kelemen BR, Mitchinson C, Wallace L, Ståhlberg J, Larenas EA. Hypocrea jecorina CEL6A protein engineering. BIOTECHNOLOGY FOR BIOFUELS 2010; 3:20. [PMID: 20822549 PMCID: PMC2945327 DOI: 10.1186/1754-6834-3-20] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 09/08/2010] [Indexed: 05/03/2023]
Abstract
The complex technology of converting lignocellulose to fuels such as ethanol has advanced rapidly over the past few years, and enzymes are a critical component of this technology. The production of effective enzyme systems at cost structures that facilitate commercial processes has been the focus of research for many years. Towards this end, the H. jecorina cellobiohydrolases, CEL7A and CEL6A, have been the subject of protein engineering at Genencor. Our first rounds of cellobiohydrolase engineering were directed towards improving the thermostability of both of these enzymes and produced variants of CEL7A and CEL6A with apparent melting temperatures above 70°C, placing their stability on par with that of H. jecorina CEL5A (EG2) and CEL3A (BGL1). We have now moved towards improving CEL6A- and CEL7A-specific performance in the context of a complete enzyme system under industrially relevant conditions. Achievement of these goals required development of new screening strategies and tools. We discuss these advances along with some results, focusing mainly on engineering of CEL6A.
Collapse
Affiliation(s)
- Suzanne E Lantz
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Frits Goedegebuur
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Ronald Hommes
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Thijs Kaper
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Bradley R Kelemen
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Colin Mitchinson
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Louise Wallace
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Jerry Ståhlberg
- Department of Molecular Biology, Swedish University of Agricultural Sciences, POB 590, SE-751 24 Uppsala, Sweden
| | - Edmundo A Larenas
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| |
Collapse
|
32
|
Rubini M, Dillon A, Kyaw C, Faria F, Poças-Fonseca M, Silva-Pereira I. Cloning, characterization and heterologous expression of the firstPenicillium echinulatumcellulase gene. J Appl Microbiol 2010; 108:1187-98. [DOI: 10.1111/j.1365-2672.2009.04528.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
33
|
Ogura K, Yamasaki M, Yamada T, Mikami B, Hashimoto W, Murata K. Crystal structure of family 14 polysaccharide lyase with pH-dependent modes of action. J Biol Chem 2010; 284:35572-9. [PMID: 19846561 DOI: 10.1074/jbc.m109.068056] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Chlorella virus enzyme vAL-1 (38 kDa), a member of polysaccharide lyase family 14, degrades the Chlorella cell wall by cleaving the glycoside bond of the glucuronate residue (GlcA) through a beta-elimination reaction. The enzyme consists of an N-terminal cell wall-attaching domain (11 kDa) and a C-terminal catalytic module (27 kDa). Here, we show the enzyme characteristics of vAL-1, especially its pH-dependent modes of action, and determine the structure of the catalytic module. vAL-1 also exhibited alginate lyase activity at alkaline pH, and truncation of the N-terminal domain increased the lyase activity by 50-fold at pH 7.0. The truncated form vAL-1(S) released di- to hexasaccharides from alginate at pH 7.0, whereas disaccharides were preferentially generated at pH 10.0. This indicates that vAL-1(S) shows two pH-dependent modes of action: endo- and exotypes. The x-ray crystal structure of vAL-1(S) at 1.2 A resolution showed two antiparallel beta-sheets with a deep cleft showing a beta-jelly roll fold. The structure of GlcA-bound vAL-1(S) at pH 7.0 and 10.0 was determined: GlcA was found to be bound outside and inside the cleft at pH 7.0 and 10.0, respectively. This suggests that the electric charges at the active site greatly influence the binding mode of substrates and regulate endo/exo activity. Site-directed mutagenesis demonstrated that vAL-1(S) has a specific amino acid arrangement distinct from other alginate lyases crucial for catalysis. This is, to our knowledge, the first study in which the structure of a family 14 polysaccharide lyase with two different modes of action has been determined.
Collapse
Affiliation(s)
- Kohei Ogura
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji 611-0011 , Japan
| | | | | | | | | | | |
Collapse
|
34
|
Cloning and heterologous expression of a novel endoglucanase gene egVIII from Trichoderma viride in Saccharomyces cerevisiae. Appl Biochem Biotechnol 2009; 162:103-15. [PMID: 19590984 DOI: 10.1007/s12010-009-8700-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 06/22/2009] [Indexed: 10/20/2022]
Abstract
Endoglucanase is a major cellulolytic enzyme produced by the fungus Trichoderma viride. The 1,317 bp cDNA of endoglucanase gene egVIII was cloned from T. viride AS3.3711, encoding a 438 amino acid protein with a calculated molecular mass of 46.86 kDa and isoelectric point of 4.32. Sequence analysis suggested that EGVIII belonged to the glycosyl hydrolase family 5. The N-terminal region of EGVIII contains a signal peptide sequence of 19 amino acid residues, indicating that it is an extracellular enzyme. Transcription of the egVIII gene in T. viride AS3.3711 can be induced by carboxymethyl cellulose sodium (CMC-Na), sucrose, microcrystalline cellulose, and corn stalk, and inhibited by glucose and fructose. The alpha-mating factor signal can effectively enhance the secretion of the recombinant EGVIII in Saccharomyces cerevisiae, as demonstrated by the enzymatic activity of recombinant yeast IpYEMalpha-xegVIII in the supernatant, which was 0.86 times higher than that of the IpYES2-egVIII. Recombinant endoglucanase EGVIII showed optimal activity at a temperature of 60 degrees C and pH of 6.0. It was stable when incubated from 35 degrees C to 70 degrees C for 1 h. The enzymatic activity of recombinant EGVIII was stable at a pH 3.0 to 7.5 at 50 degrees C and reached the highest level at 0.174U when activated by 75 mM of Zn(2+). The Michaelis-Menten constant (Km) and Kcat values for CMC-Na and cellotriose hydrolysis were 3.82 mg/ml, 9.56 s(-1) and 1.75 mg/ml, 7.08 s(-1), respectively. Transgenic yeast strain IpYEMalpha-xegVIII might be useful for renewable fuels industries.
Collapse
|
35
|
Ochiai A, Itoh T, Mikami B, Hashimoto W, Murata K. Structural determinants responsible for substrate recognition and mode of action in family 11 polysaccharide lyases. J Biol Chem 2009; 284:10181-9. [PMID: 19193638 PMCID: PMC2665072 DOI: 10.1074/jbc.m807799200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 12/29/2008] [Indexed: 11/06/2022] Open
Abstract
A saprophytic Bacillus subtilis secretes two types of rhamnogalacturonan (RG) lyases, endotype YesW and exotype YesX, which are responsible for an initial cleavage of the RG type I (RG-I) region of plant cell wall pectin. Polysaccharide lyase family 11 YesW and YesX with a significant sequence identity (67.8%) cleave glycoside bonds between rhamnose and galacturonic acid residues in RG-I through a beta-elimination reaction. Here we show the structural determinants for substrate recognition and the mode of action in polysaccharide lyase family 11 lyases. The crystal structures of YesW in complex with rhamnose and ligand-free YesX were determined at 1.32 and 1.65 A resolution, respectively. The YesW amino acid residues such as Asn(152), Asp(172), Asn(532), Gly(533), Thr(534), and Tyr(595) in the active cleft bind to rhamnose molecules through hydrogen bonds and van der Waals contacts. Other rhamnose molecules are accommodated at the noncatalytic domain far from the active cleft, revealing that the domain possibly functions as a novel carbohydrate-binding module. A structural comparison between YesW and YesX indicates that a specific loop in YesX for recognizing the terminal saccharide molecule sterically inhibits penetration of the polymer over the active cleft. The loop-deficient YesX mutant exhibits YesW-like endotype activity, demonstrating that molecular conversion regarding the mode of action is achieved by the addition/removal of the loop for recognizing the terminal saccharide. This is the first report on a structural insight into RG-I recognition and molecular conversion of exotype to endotype in polysaccharide lyases.
Collapse
|
36
|
Cartmell A, Topakas E, Ducros VMA, Suits MDL, Davies GJ, Gilbert HJ. The Cellvibrio japonicus mannanase CjMan26C displays a unique exo-mode of action that is conferred by subtle changes to the distal region of the active site. J Biol Chem 2008; 283:34403-13. [PMID: 18799462 PMCID: PMC2662245 DOI: 10.1074/jbc.m804053200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 08/11/2008] [Indexed: 11/06/2022] Open
Abstract
The microbial degradation of the plant cell wall is a pivotal biological process that is of increasing industrial significance. One of the major plant structural polysaccharides is mannan, a beta-1,4-linked d-mannose polymer, which is hydrolyzed by endo- and exo-acting mannanases. The mechanisms by which the exo-acting enzymes target the chain ends of mannan and how galactose decorations influence activity are poorly understood. Here we report the crystal structure and biochemical properties of CjMan26C, a Cellvibrio japonicus GH26 mannanase. The exo-acting enzyme releases the disaccharide mannobiose from the nonreducing end of mannan and mannooligosaccharides, harnessing four mannose-binding subsites extending from -2 to +2. The structure of CjMan26C is very similar to that of the endo-acting C. japonicus mannanase CjMan26A. The exo-activity displayed by CjMan26C, however, reflects a subtle change in surface topography in which a four-residue extension of surface loop creates a steric block at the distal glycone -2 subsite. endo-Activity can be introduced into enzyme variants through truncation of an aspartate side chain, a component of a surface loop, or by removing both the aspartate and its flanking residues. The structure of catalytically competent CjMan26C, in complex with a decorated manno-oligosaccharide, reveals a predominantly unhydrolyzed substrate in an approximate (1)S(5) conformation. The complex structure helps to explain how the substrate "side chain" decorations greatly reduce the activity of the enzyme; the galactose side chain at the -1 subsite makes polar interactions with the aglycone mannose, possibly leading to suboptimal binding and impaired leaving group departure. This report reveals how subtle differences in the loops surrounding the active site of a glycoside hydrolase can lead to a change in the mode of action of the enzyme.
Collapse
Affiliation(s)
- Alan Cartmell
- Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom
| | | | | | | | | | | |
Collapse
|
37
|
Yao YY, Shrestha KL, Wu YJ, Tasi HJ, Chen CC, Yang JM, Ando A, Cheng CY, Li YK. Structural simulation and protein engineering to convert an endo-chitosanase to an exo-chitosanase. Protein Eng Des Sel 2008; 21:561-6. [DOI: 10.1093/protein/gzn033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
38
|
Qin Y, Wei X, Liu X, Wang T, Qu Y. Purification and characterization of recombinant endoglucanase of Trichoderma reesei expressed in Saccharomyces cerevisiae with higher glycosylation and stability. Protein Expr Purif 2008; 58:162-7. [DOI: 10.1016/j.pep.2007.09.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 07/22/2007] [Accepted: 09/04/2007] [Indexed: 10/22/2022]
|
39
|
Mertz B, Hill AD, Mulakala C, Reilly PJ. Automated docking to explore subsite binding by glycoside hydrolase family 6 cellobiohydrolases and endoglucanases. Biopolymers 2007; 87:249-60. [PMID: 17724729 DOI: 10.1002/bip.20831] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cellooligosaccharides were computationally docked using AutoDock into the active sites of the glycoside hydrolase Family 6 enzymes Hypocrea jecorina (formerly Trichoderma reesei) cellobiohydrolase and Thermobifida fusca endoglucanase. Subsite -2 exerts the greatest intermolecular energy in binding beta-glucosyl residues, with energies progressively decreasing to either side. Cumulative forces imparting processivity exerted by these two enzymes are significantly less than by the equivalent glycoside hydrolase Family 7 enzymes studied previously. Putative subsites -4, -3, +3, and +4 exist in H. jecorina cellobiohydrolase, along with putative subsites -4, -3, and +3 in T. fusca endoglucanase, but they are less important than subsites -2, -1, +1, and +2. In general, binding adds 3-7 kcal/mol to ligand intramolecular energies because of twisting of scissile glycosidic bonds. Distortion of beta-glucosyl residues to the (2)S(O) conformation by binding in subsite -1 adds approximately 7 kcal/mol to substrate intramolecular energies.
Collapse
Affiliation(s)
- Blake Mertz
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA
| | | | | | | |
Collapse
|
40
|
Sikorski P, Sørbotten A, Horn SJ, Eijsink VGH, Vårum KM. Serratia marcescens chitinases with tunnel-shaped substrate-binding grooves show endo activity and different degrees of processivity during enzymatic hydrolysis of chitosan. Biochemistry 2006; 45:9566-74. [PMID: 16878991 DOI: 10.1021/bi060370l] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The modes of action of three family 18 chitinases (ChiA, ChiB, and ChiC) from Serratia marcescens during the degradation of a water-soluble polymeric substrate, chitosan, were investigated using a combination of viscosity measurements, reducing end assays, and characterization of the size-distribution of the oligomeric products. All three enzymes yielded a fast reduction in molecular weight of the chitosan substrate at a very early stage of hydrolysis, which is typical for endo-acting enzymes. For ChiA and ChiB, this is inconsistent with the previously proposed exo-attack mode of action. The main difference between ChiA, ChiB, and ChiC is the degree of processivity. ChiC is an endo enzyme with no apparent processivity. ChiA and ChiB are processive enzymes in which the substrate remains bound to the active cleft after successful hydrolysis and is moved along for the next hydrolysis to occur. ChiA and ChiB perform on average 9.1 and 3.4 cleavages, respectively, for the formation of each enzyme-substrate complex. ChiA and ChiB have deep, tunnel-like substrate-binding grooves. The demonstration of endo activity shows that substrate binding must involve the temporary restructuring of the loops that make up the roofs of the substrate-binding grooves, similar to what has been proposed for cellobiohydrolase Cel6A. The data suggest that the exo-type of activity observed for ChiA and ChiB during the degradation of solid crystalline chitin is due to the better accessibility of chain ends, rather than intrinsic enzyme properties.
Collapse
Affiliation(s)
- Pawel Sikorski
- Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
| | | | | | | | | |
Collapse
|
41
|
Horn SJ, Sørbotten A, Synstad B, Sikorski P, Sørlie M, Vårum KM, Eijsink VGH. Endo/exo mechanism and processivity of family 18 chitinases produced by Serratia marcescens. FEBS J 2006; 273:491-503. [PMID: 16420473 DOI: 10.1111/j.1742-4658.2005.05079.x] [Citation(s) in RCA: 206] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We present a comparative study of ChiA, ChiB, and ChiC, the three family 18 chitinases produced by Serratia marcescens. All three enzymes eventually converted chitin to N-acetylglucosamine dimers (GlcNAc2) and a minor fraction of monomers. ChiC differed from ChiA and ChiB in that it initially produced longer oligosaccharides from chitin and had lower activity towards an oligomeric substrate, GlcNAc6. ChiA and ChiB could convert GlcNAc6 directly to three dimers, whereas ChiC produced equal amounts of tetramers and dimers, suggesting that the former two enzymes can act processively. Further insight was obtained by studying degradation of the soluble, partly deacetylated chitin-derivative chitosan. Because there exist nonproductive binding modes for this substrate, it was possible to discriminate between independent binding events and processive binding events. In reactions with ChiA and ChiB the polymer disappeared very slowly, while the initially produced oligomers almost exclusively had even-numbered chain lengths in the 2-12 range. This demonstrates a processive mode of action in which the substrate chain moves by two sugar units at a time, regardless of whether complexes formed along the way are productive. In contrast, reactions with ChiC showed rapid disappearance of the polymer and production of a continuum of odd- and even-numbered oligomers. These results are discussed in the light of recent literature data on directionality and synergistic effects of ChiA, ChiB and ChiC, leading to the conclusion that ChiA and ChiB are processive chitinases that degrade chitin chains in opposite directions, while ChiC is a nonprocessive endochitinase.
Collapse
Affiliation(s)
- Svein J Horn
- Department of Chemistry, Biotechnology and Food Science, the Norwegian University of Life Sciences, As, Norway
| | | | | | | | | | | | | |
Collapse
|
42
|
Mertz B, Kuczenski RS, Larsen RT, Hill AD, Reilly PJ. Phylogenetic analysis of family 6 glycoside hydrolases. Biopolymers 2005; 79:197-206. [PMID: 16086389 DOI: 10.1002/bip.20347] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Multiple sequence alignment separates members of glycoside hydrolase Family 6 into eight subfamilies: one of mainly actinobacterial endoglucanases (EGs), one of ascomycotal EGs, one of chytridiomycotal EGs and cellobiohydrolases (CBHs), one of actinobacterial and proteobacterial CBHs, one of chytridiomycotal CBHs, two of ascomycotal CBHs, and one of basidiomycotal CBHs. Each also has some proteins of unknown function. Multiple sequence alignment also extends to all of Family 6 the observation that lengths of loops that form the active-site tunnel in CBHs vary among subfamilies, and along with loop conformations, determine enzyme function.
Collapse
Affiliation(s)
- Blake Mertz
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA
| | | | | | | | | |
Collapse
|
43
|
Nakamura I, Yoneda H, Maeda T, Makino A, Ohmae M, Sugiyama J, Ueda M, Kobayashi S, Kimura S. Enzymatic Polymerization Behavior Using Cellulose-Binding Domain Deficient Endoglucanase II. Macromol Biosci 2005; 5:623-8. [PMID: 15988789 DOI: 10.1002/mabi.200500044] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A mutant enzyme, EGII(core), in which the cellulose-binding domain was deleted from endoglucanase II from Trichoderma viride, was expressed in yeast, and the secreted enzyme was examined for the enzymatic polymerization to obtain artificial cellulose. EGII(core) polymerized beta-cellobiosyl fluoride to afford crystalline cellulose of type II. Comparison of the polymerization behavior of EGII(core) with that of EGII revealed the following: i) the crystalline product obtained with EGII(core) was stable in the polymerization solution, although the product was readily hydrolyzed in the presence of EGII; ii) the turnover number of EGII(core) was as high as that of EGII; iii) EGII(core) produced highly crystalline cellulose. EGII(core) is therefore advantageous for enzymatic polymerization.
Collapse
Affiliation(s)
- Itsuko Nakamura
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Wang T, Liu X, Yu Q, Zhang X, Qu Y, Gao P, Wang T. Directed evolution for engineering pH profile of endoglucanase III from Trichoderma reesei. ACTA ACUST UNITED AC 2005; 22:89-94. [PMID: 15857788 DOI: 10.1016/j.bioeng.2004.10.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Revised: 10/22/2004] [Accepted: 10/25/2004] [Indexed: 10/25/2022]
Abstract
The potential of cellulase has been revealed not only in biomass conversion but also in various industrial processes, including food, textiles, laundry, pulp, and paper. Due to the need for alkali-tolerant cellulase with high specific activity at alkaline pH, for example, for application in detergent industry an error-prone PCR approach was employed for enhancing the alkali-tolerant ability of endoglucanase III (EG III) from Trichoderma reesei by error-prone PCR. One mutant (N321T) which exhibited an optimal activity at pH 5.4, corresponded to a basic shift of 0.6 pH unit compared to the wild-type enzyme, was selected and characterized. In addition, two site-directed mutations, N321D and N321H, were designed to study the role of residue at position 321. As expected, the N321D mutation changed enzyme's optimal activity to pH 4.0, resulting in a large decrease in the specific activity. However, the N321H mutated enzyme was active over a broader pH range compared to the wild type, with no much change in the specific activity. These properties suggest that the residue at position 321 is important amino acid residue in determining the pH activity profile of the EG III from T. reesei.
Collapse
Affiliation(s)
- Ting Wang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China
| | | | | | | | | | | | | |
Collapse
|
45
|
Zhang YHP, Lynd LR. Toward an aggregated understanding of enzymatic hydrolysis of cellulose: noncomplexed cellulase systems. Biotechnol Bioeng 2005; 88:797-824. [PMID: 15538721 DOI: 10.1002/bit.20282] [Citation(s) in RCA: 883] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Information pertaining to enzymatic hydrolysis of cellulose by noncomplexed cellulase enzyme systems is reviewed with a particular emphasis on development of aggregated understanding incorporating substrate features in addition to concentration and multiple cellulase components. Topics considered include properties of cellulose, adsorption, cellulose hydrolysis, and quantitative models. A classification scheme is proposed for quantitative models for enzymatic hydrolysis of cellulose based on the number of solubilizing activities and substrate state variables included. We suggest that it is timely to revisit and reinvigorate functional modeling of cellulose hydrolysis, and that this would be highly beneficial if not necessary in order to bring to bear the large volume of information available on cellulase components on the primary applications that motivate interest in the subject.
Collapse
|
46
|
Proctor MR, Taylor EJ, Nurizzo D, Turkenburg JP, Lloyd RM, Vardakou M, Davies GJ, Gilbert HJ. Tailored catalysts for plant cell-wall degradation: redesigning the exo/endo preference of Cellvibrio japonicus arabinanase 43A. Proc Natl Acad Sci U S A 2005; 102:2697-702. [PMID: 15708971 PMCID: PMC549454 DOI: 10.1073/pnas.0500051102] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Indexed: 11/18/2022] Open
Abstract
Enzymes acting on polymeric substrates are frequently classified as exo or endo, reflecting their preference for, or ignorance of, polymer chain ends. Most biotechnological applications, especially in the field of polysaccharide degradation, require either endo- or exo-acting hydrolases, or they harness the essential synergy between these two modes of action. Here, we have used genomic data in tandem with structure to modify, radically, the chain-end specificity of the Cellvibrio japonicus exo-arabinanase CjArb43A. The structure of Bacillus subtilis endo-arabinanase 43A (BsArb43A) in harness with chain-end recognition kinetics of CjArb43A directed a rational design approach that led to the conversion of the Cellvibrio enzyme from an exo to an endo mode of action. One of the exo-acting mutants, D35L/Q316A, displays similar activity to WT CjArb43A and the removal of the steric block mediated by the side chains of Gln-316 and Asp-53 at the -3 subsite confers its capacity to attack internal glycoside bonds. This study provides a template for the production of tailored industrial catalysts. The introduction of subtle changes informed by comparative 3D structural and genomic data can lead to fundamental changes in the mode of action of these enzymes.
Collapse
Affiliation(s)
- Mark R Proctor
- Institute for Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kindgom
| | | | | | | | | | | | | | | |
Collapse
|
47
|
von Ossowski I, Ståhlberg J, Koivula A, Piens K, Becker D, Boer H, Harle R, Harris M, Divne C, Mahdi S, Zhao Y, Driguez H, Claeyssens M, Sinnott ML, Teeri TT. Engineering the Exo-loop of Trichoderma reesei Cellobiohydrolase, Cel7A. A comparison with Phanerochaete chrysosporium Cel7D. J Mol Biol 2003; 333:817-29. [PMID: 14568538 DOI: 10.1016/s0022-2836(03)00881-7] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The exo-loop of Trichoderma reesei cellobiohydrolase Cel7A forms the roof of the active site tunnel at the catalytic centre. Mutants were designed to study the role of this loop in crystalline cellulose degradation. A hydrogen bond to substrate made by a tyrosine at the tip of the loop was removed by the Y247F mutation. The mobility of the loop was reduced by introducing a new disulphide bridge in the mutant D241C/D249C. The tip of the loop was deleted in mutant Delta(G245-Y252). No major structural disturbances were observed in the mutant enzymes, nor was the thermostability of the enzyme affected by the mutations. The Y247F mutation caused a slight k(cat) reduction on 4-nitrophenyl lactoside, but only a small effect on cellulose hydrolysis. Deletion of the tip of the loop increased both k(cat) and K(M) and gave reduced product inhibition. Increased activity was observed on amorphous cellulose, while only half the original activity remained on crystalline cellulose. Stabilisation of the exo-loop by the disulphide bridge enhanced the activity on both amorphous and crystalline cellulose. The ratio Glc(2)/(Glc(3)+Glc(1)) released from cellulose, which is indicative of processive action, was highest with Tr Cel7A wild-type enzyme and smallest with the deletion mutant on both substrates. Based on these data it seems that the exo-loop of Tr Cel7A has evolved to facilitate processive crystalline cellulose degradation, which does not require significant conformational changes of this loop.
Collapse
|
48
|
Boer H, Koivula A. The relationship between thermal stability and pH optimum studied with wild-type and mutant Trichoderma reesei cellobiohydrolase Cel7A. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:841-8. [PMID: 12603317 DOI: 10.1046/j.1432-1033.2003.03431.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The major cellulase secreted by the filamentous fungus Trichoderma reesei is cellobiohydrolase Cel7A. Its three-dimensional structure has been solved and various mutant enzymes produced. In order to study the potential use of T. reesei Cel7A in the alkaline pH range, the thermal stability of Cel7A was studied as a function of pH with the wild-type and two mutant enzymes using different spectroscopic methods. Tryptophan fluorescence and CD measurements of the wild-type enzyme show an optimal thermostability between pH 3.5-5.6 (Tm, 62 +/- 2 degrees C), at which the highest enzymatic activity is also observed, and a gradual decrease in the stability at more alkaline pH values. A soluble substrate, cellotetraose, was shown to stabilize the protein fold both at optimal and alkaline pH. In addition, unfolding of the Cel7A enzyme and the release of the substrate seem to coincide at both acidic and alkaline pH, demonstrated by a change in the fluorescence emission maximum. CD measurements were used to show that the five point mutations (E223S/A224H/L225V/T226A/D262G) that together result in a more alkaline pH optimum [Becker, D., Braet, C., Brumer, H., III, Claeyssens, M., Divne, C., Fagerström, R.B., Harris, M., Jones, T.A., Kleywegt, G.J., Koivula, A., et al. (2001) Biochem. J.356, 19-30], destabilize the protein fold both at acidic and alkaline pH when compared with the wild-type enzyme. In addition, an interesting time-dependent fluorescence change, which was not observed by CD, was detected for the pH mutant. Our data show that in order to engineer more alkaline pH cellulases, a combination of mutations should be found, which both shift the pH optimum and at the same time improve the thermal stability at alkaline pH range.
Collapse
Affiliation(s)
- Harry Boer
- VTT Biotechnology, PO Box 1500, Espoo, Finland.
| | | |
Collapse
|
49
|
Michel G, Chantalat L, Duee E, Barbeyron T, Henrissat B, Kloareg B, Dideberg O. The kappa-carrageenase of P. carrageenovora features a tunnel-shaped active site: a novel insight in the evolution of Clan-B glycoside hydrolases. Structure 2001; 9:513-25. [PMID: 11435116 DOI: 10.1016/s0969-2126(01)00612-8] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND kappa-carrageenans are gel-forming, sulfated 1,3-alpha-1,4-beta-galactans from the cell walls of marine red algae. The kappa-carrageenase from the marine, gram-negative bacterium Pseudoalteromonas carrageenovora degrades kappa-carrageenan both in solution and in solid state by an endoprocessive mechanism. This beta-galactanase belongs to the clan-B of glycoside hydrolases. RESULTS The structure of P. carrageenovora kappa-carrageenase has been solved to 1.54 A resolution by the multiwavelength anomalous diffraction (MAD) method, using a seleno-methionine-substituted form of the enzyme. The enzyme folds into a curved beta sandwich, with a tunnel-like active site cavity. Another remarkable characteristic is the presence of an arginine residue at subsite -1. CONCLUSIONS The crystal structure of P. carrageenovora kappa-carrageenase is the first three-dimensional structure of a carrageenase. Its tunnel-shaped active site, the first to be reported for enzymes other than cellulases, suggests that such tunnels are associated with the degradation of solid polysaccharides. Clan-B glycoside hydrolases fall into two subgroups, one with catalytic machinery held by an ancestral beta bulge, and the other in which it is held by a regular beta strand. At subsite -1, all of these hydrolases exhibit an aromatic amino acid that interacts with the hexopyranose ring of the monosaccharide undergoing catalysis. In addition, in kappa-carrageenases, an arginine residue recognizes the sulfate-ester substituents of the beta-linked kappa-carrageenan monomers. It also appears that, in addition to the nucleophile and acid/base catalysts, two other amino acids are involved with the catalytic cycle, accelerating the deglycosylation step.
Collapse
Affiliation(s)
- G Michel
- Laboratoire de Cristallographie Macromoléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, CNRS/CEA, 41 Avenue des Martyrs, 38027 Cedex 1, Grenoble, France
| | | | | | | | | | | | | |
Collapse
|
50
|
Abstract
Cellulases are enzymes which hydrolyse the beta-1,4-glucosidic linkages of cellulose. They fall into 13 of the 82 glycoside hydrolase families identified by sequence analysis, but they are traditionally divided into two classes termed 'endoglucanases' (EC 3.2.1.4) and 'cellobiohydrolases' (3.2.1.91). Both types of cellulases degrade soluble cellodextrins and amorphous cellulose but, with a few notable exceptions, it is only the cellobiohydrolases which degrade crystalline cellulose efficiently. Site-directed mutagenesis has been central to the characterisation of cellulases, ranging from the identification and characterisation of putative catalytic and binding residues, the trapping of enzyme-substrate complexes by crystallography through to the construction of new and improved biocatalysts including 'glycosynthases'. Whilst studies on soluble substrates and substrate analogues have provided a wealth of information, understanding the mechanism of degradation of the natural substrate, crystalline cellulose, remains a great challenge.
Collapse
Affiliation(s)
- M Schülein
- Novozymes A/S, Smoermosevej 25, DK-2880, Bagsvaerd, Denmark.
| |
Collapse
|