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Guo Y, Chen A, Liu K, Ji C. Structural insights and functional characterization of a novel β-glucosidase derived from Thermotoga profunda. Biochem Biophys Res Commun 2024; 732:150405. [PMID: 39033552 DOI: 10.1016/j.bbrc.2024.150405] [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: 03/15/2024] [Revised: 06/20/2024] [Accepted: 07/12/2024] [Indexed: 07/23/2024]
Abstract
β-Glucosidase is a crucial cellulase, as its activity determines the efficiency of cellulose hydrolysis into glucose. This study addresses the functional and structural characteristics of Thermotoga profunda β-glucosidase (Tp-BGL). Tp-BGL exhibited a Km of 0.3798 mM for p-nitrophenyl-β-d-glucopyranoside (pNPGlc) and 4.44 mM for cellobiose, with kcat/Km of 1211.16 and 4.18 s-1 mM-1, respectively. In addition, Tp-BGL showed significant pH adaptability and thermal stability, with a Tm of 85.7 °C and retaining >90 % of its activity after incubation at 80 °C for 90 min. The crystal structure of Tp-BGL was resolved at 1.95 Å resolution, and reveals a typical TIM barrel structure. Comparative structural analysis highlighted that the major distinction between Tp-BGL and the other glucosidases lies in their loop regions.
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Affiliation(s)
- Yanchao Guo
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Anke Chen
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Kelin Liu
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Chaoneng Ji
- School of Life Sciences, Fudan University, Shanghai, 200433, China.
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2
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Magwaza B, Amobonye A, Pillai S. Microbial β-glucosidases: Recent advances and applications. Biochimie 2024; 225:49-67. [PMID: 38734124 DOI: 10.1016/j.biochi.2024.05.009] [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: 02/22/2024] [Revised: 04/05/2024] [Accepted: 05/06/2024] [Indexed: 05/13/2024]
Abstract
The global β-glucosidase market is currently estimated at ∼400 million USD, and it is expected to double in the next six years; a trend that is mainly ascribed to the demand for the enzyme for biofuel processing. Microbial β-glucosidase, particularly, has thus garnered significant attention due to its ease of production, catalytic efficiency, and versatility, which have all facilitated its biotechnological potential across different industries. Hence, there are continued efforts to screen, produce, purify, characterize and evaluate the industrial applicability of β-glucosidase from actinomycetes, bacteria, fungi, and yeasts. With this rising demand for β-glucosidase, various cost-effective and efficient approaches are being explored to discover, redesign, and enhance their production and functional properties. Thus, this present review provides an up-to-date overview of advancements in the utilization of microbial β-glucosidases as "Emerging Green Tools" in 21st-century industries. In this regard, focus was placed on the use of recombinant technology, protein engineering, and immobilization techniques targeted at improving the industrial applicability of the enzyme. Furthermore, insights were given into the recent progress made in conventional β-glucosidase production, their industrial applications, as well as the current commercial status-with a focus on the patents.
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Affiliation(s)
- Buka Magwaza
- Department of Biotechnology and Food Science, Faculty of Applied Sciences, Durban University of Technology, P. O. Box 1334, Durban, 4000, South Africa.
| | - Ayodeji Amobonye
- Department of Biotechnology and Food Science, Faculty of Applied Sciences, Durban University of Technology, P. O. Box 1334, Durban, 4000, South Africa.
| | - Santhosh Pillai
- Department of Biotechnology and Food Science, Faculty of Applied Sciences, Durban University of Technology, P. O. Box 1334, Durban, 4000, South Africa.
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3
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Kamande SM, Omwenga GI, Ngugi MP. Production of cellulases by Xylaria sp. and Nemania sp. using lignocellulose substrates for bioethanol production from maize cobs. Heliyon 2024; 10:e36802. [PMID: 39296107 PMCID: PMC11408009 DOI: 10.1016/j.heliyon.2024.e36802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Revised: 08/22/2024] [Accepted: 08/22/2024] [Indexed: 09/21/2024] Open
Abstract
Two species of Xylaria (KM01, KM03) and Nemania sp.KM02 isolated from decaying plant biomass were evaluated for their ability to produce cellulases on maize cob, eucalyptus, and cypress substrates under solid-state fermentation. A total of 10 fungal samples from decaying plant biomass were collected from Karura forest based on morphological variations. The fungi isolated were screened for cellulase activity and positive isolates were selected for the study. ITS4 R and ITS86 F primers were used to identify the fungal isolates with accuracy ranging from 98 % to 100 %. The crude cellulases produced was assayed for FPase, exoglucanase, endoglucanase and β-glucosidase. Cellulases of Xylaria sp. KM01 produced higher FPase and exoglucanase (2.01 ± 0.13 IU/ml and 0.94 ± 0.08 IU/ml) on pretreated maize cobs with 0.1M HCl at 121oC, while that of Xylaria sp.KM03 produced higher β-glucosidase and endoglucanase (588.6 ± 64.2 IU/ml and 3.59 ± 0.02 IU/ml) on maize cobs pretreated with 0.1M NaOH at 121oC. However, cellulases of Xylaria sp. KM01 produced higher β-glucosidase and FPase (629.7 ± 20.2 IU/ml and 1.67 ± 0.03 IU/ml) on untreated maize cobs after the 9th day of incubation, whereas cellulases of Xylaria sp.KM03 and Nemania sp.KM02 produced higher endoglucanase and exoglucanase (2.80 ± 0.21 IU/ml and 0.83 ± 0.02 IU/ml) on untreated maize cobs after the 3rd and 6th day of incubation. Saccharification of maize cobs by cellulase of Xylaria sp.KM03 produced the highest reducing sugars at 8 % substrate loading (10.17 ± 0.37 mg/ml) after 72 h of incubation. Simultaneous hydrolysis and fermentation of maize cobs by cellulase of Nemania sp.KM02 and Saccharomyces cerevisiae yielded higher bioethanol (28.72 ± 3.82 mg/ml) after 96 h of fermentation. Maize cob is established as a suitable feedstock for cellulases and bioethanol production.
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Affiliation(s)
- Stephen M Kamande
- Technical University of Kenya, Department of Biochemistry and Biotechnology, P.O. Box 52428-00200, Nairobi, Kenya
- Kenyatta University, Department of Biochemistry, Biotechnology and Microbiology, P.O. Box 43844-00100, Nairobi, Kenya
| | - George I Omwenga
- Kenyatta University, Department of Biochemistry, Biotechnology and Microbiology, P.O. Box 43844-00100, Nairobi, Kenya
| | - Mathew P Ngugi
- Kenyatta University, Department of Biochemistry, Biotechnology and Microbiology, P.O. Box 43844-00100, Nairobi, Kenya
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Potkule JB, Kahar SP, Kumar M, Annapure US. Impact of non-thermal techniques on enzyme modifications for their applications in food. Int J Biol Macromol 2024; 275:133566. [PMID: 38960264 DOI: 10.1016/j.ijbiomac.2024.133566] [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: 06/05/2024] [Accepted: 06/28/2024] [Indexed: 07/05/2024]
Abstract
The present review elaborates on the details of the enzyme, its structure, specificity, and the mechanism of action of selected enzymes as well as structural changes and loss or gain of activity after non-thermal treatments for food-based applications. Enzymes are biological catalysts found in various systems such as plants, animals, and microorganisms. Most of the enzymes have their optimum pH, temperature, and substrate or group of substrates. The conformational modification of enzymes either increases or decreases the rate of reaction at different pH, and temperature conditions. Enzymes are modified by different techniques to enhance the activity of enzymes for their commercial applications mainly due to the high cost of enzymes, stability, and difficulties that occur during the use of enzymes in different conditions. On the opposite, enzyme inactivation provides its application to extend the shelf life of fruits and vegetables by denaturation and partial inactivation of enzymes. Hence, the activation and inactivation of enzymes are studied by non-thermal techniques in both the model and the food system. The highly reactive species generated during non-thermal techniques cause chemical and structural modification. The enzyme modifications depend on the type and source of the enzyme, type of technique, and the parameters used.
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Affiliation(s)
- Jayashree B Potkule
- Department of Food Engineering and Technology, Institute of Chemical Technology, Matunga, Mumbai, India
| | - Suraj P Kahar
- Department of Food Engineering and Technology, Institute of Chemical Technology, Matunga, Mumbai, India
| | - Manoj Kumar
- Chemical and Biochemical Processing Division, ICAR - Central Institute for Research on Cotton Technology, Matunga, Mumbai, India
| | - Uday S Annapure
- Department of Food Engineering and Technology, Institute of Chemical Technology, Matunga, Mumbai, India; Institute of Chemical Technology, Marathwada Campus, Jalna, India.
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de Andrades D, Alnoch RC, Alves GS, Salgado JCS, Almeida PZ, Berto GL, Segato F, Ward RJ, Buckeridge MS, Polizeli MDLTM. Recombinant GH3 β-glucosidase stimulated by xylose and tolerant to furfural and 5-hydroxymethylfurfural obtained from Aspergillus nidulans. BIORESOUR BIOPROCESS 2024; 11:77. [PMID: 39073555 PMCID: PMC11286919 DOI: 10.1186/s40643-024-00784-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 07/03/2024] [Indexed: 07/30/2024] Open
Abstract
The β-glucosidase gene from Aspergillus nidulans FGSC A4 was cloned and overexpressed in the A. nidulans A773. The resulting purified β-glucosidase, named AnGH3, is a monomeric enzyme with a molecular weight of approximately 80 kDa, as confirmed by SDS-PAGE. Circular dichroism further validated its unique canonical barrel fold (β/α), a feature also observed in the 3D homology model of AnGH3. The most striking aspect of this recombinant enzyme is its robustness, as it retained 100% activity after 24 h of incubation at 45 and 50 ºC and pH 6.0. Even at 55 °C, it maintained 72% of its enzymatic activity after 6 h of incubation at the same pH. The kinetic parameters Vmax, KM, and Kcat/KM for ρ-nitrophenyl-β-D-glucopyranoside (ρNPG) and cellobiose were also determined. Using ρNPG, the enzyme demonstrated a Vmax of 212 U mg - 1, KM of 0.0607 mmol L - 1, and Kcat/KM of 4521 mmol L - 1 s - 1 when incubated at pH 6.0 and 65 °C. The KM, Vmax, and Kcat/KM using cellobiose were 2.7 mmol L - 1, 57 U mg - 1, and 27 mmol -1 s - 1, respectively. AnGH3 activity was significantly enhanced by xylose and ethanol at concentrations up to 1.5 mol L - 1 and 25%, respectively. Even in challenging conditions, at 65 °C and pH 6.0, the enzyme maintained its activity, retaining 100% and 70% of its initial activity in the presence of 200 mmol L - 1 furfural and 5-hydroxymethylfurfural (HMF), respectively. The potential of this enzyme was further demonstrated by its application in the saccharification of the forage grass Panicum maximum, where it led to a 48% increase in glucose release after 24 h. These unique characteristics, including high catalytic performance, good thermal stability in hydrolysis temperature, and tolerance to elevated concentrations of ethanol, D-xylose, furfural, and HMF, position this recombinant enzyme as a promising tool in the hydrolysis of lignocellulosic biomass as part of an efficient multi-enzyme cocktail, thereby opening new avenues in the field of biotechnology and enzymology.
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Affiliation(s)
- Diandra de Andrades
- Department of Biology, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
| | - Robson C Alnoch
- Department of Biology, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
- Department of Biochemistry and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - Gabriela S Alves
- Department of Biochemistry and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
- Laboratory of Enzymology and Molecular Biology of Microorganisms, Institute of Biology, Campinas State University (UNICAMP), Campinas, 13083-970, SP, Brazil
| | - Jose C S Salgado
- Department of Biology, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
- Department of Chemistry, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
| | - Paula Z Almeida
- Department of Biochemistry and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - Gabriela Leila Berto
- Department of Biotechnology, Lorena School of Engineering, University of São Paulo, Lorena, 12602-810, Brazil
| | - Fernando Segato
- Department of Biotechnology, Lorena School of Engineering, University of São Paulo, Lorena, 12602-810, Brazil
| | - Richard J Ward
- Department of Chemistry, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
| | | | - Maria de Lourdes T M Polizeli
- Department of Biology, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-901, Brazil.
- Department of Biochemistry and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil.
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Erkanli ME, El-Halabi K, Kang TK, Kim JR. Hotspot Wizard-informed engineering of a hyperthermophilic β-glucosidase for enhanced enzyme activity at low temperatures. Biotechnol Bioeng 2024; 121:2079-2090. [PMID: 38682557 DOI: 10.1002/bit.28732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 04/11/2024] [Accepted: 04/19/2024] [Indexed: 05/01/2024]
Abstract
Hyperthermophilic enzymes serve as an important source of industrial enzymes due to their high thermostability. Unfortunately, most hyperthermophilic enzymes suffer from reduced activity at low temperatures (e.g., ambient temperature), limiting their applicability. In addition, evolving hyperthermophilic enzymes to increase low temperature activity without compromising other desired properties is generally difficult. In the current study, a variant of β-glucosidase from Pyrococcus furiosus (PfBGL) was engineered to enhance enzyme activity at low temperatures through the construction of a saturation mutagenesis library guided by the HotSpot Wizard analysis, followed by its screening for activity and thermostability. From this library construction and screening, one PfBGL mutant, PfBGL-A4 containing Q214S/A264S/F344I mutations, showed an over twofold increase in β-glucosidase activity at 25 and 50°C compared to the wild type, without compromising high-temperature activity, thermostability and substrate specificity. Our experimental and computational characterizations suggest that the findings with PfBGL-A4 may be due to the elevation of local conformational flexibility around the active site, while slightly compacting the global protein structure. This study showcases the potential of HotSpot Wizard-informed engineering of hyperthermophilic enzymes and underscores the interplays among temperature, enzyme activity, and conformational flexibility in these enzymes.
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Affiliation(s)
- Mehmet Emre Erkanli
- Department of Chemical and Biomolecular Engineering, New York University, Brooklyn, New York, USA
| | - Khalid El-Halabi
- Department of Chemical and Biomolecular Engineering, New York University, Brooklyn, New York, USA
| | - Ted Keunsil Kang
- Department of Chemical and Biomolecular Engineering, New York University, Brooklyn, New York, USA
| | - Jin Ryoun Kim
- Department of Chemical and Biomolecular Engineering, New York University, Brooklyn, New York, USA
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He J, Duan J, Yu P, Li Y, Wang M, Zhang X, Chen Z, Shi P. Characterization of a novel cold-adapted GH1 β-glucosidase from Psychrobacillus glaciei and its application in the hydrolysis of soybean isoflavone glycosides. Curr Res Food Sci 2024; 8:100777. [PMID: 38840809 PMCID: PMC11150966 DOI: 10.1016/j.crfs.2024.100777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 05/16/2024] [Accepted: 05/23/2024] [Indexed: 06/07/2024] Open
Abstract
The novel β-glucosidase gene (pgbgl1) of glycoside hydrolase (GH) family 1 from the psychrotrophic bacterium Psychrobacillus glaciei sp. PB01 was successfully expressed in Escherichia coli BL21 (DE3). The deduced PgBgl1 contained 447 amino acid residues with a calculated molecular mass of 51.4 kDa. PgBgl1 showed its maximum activity at pH 7.0 and 40 °C, and still retained over 10% activity at 0 °C, suggesting that the recombinant PgBgl1 is a cold-adapted enzyme. The substrate specificity, Km, Vmax, and Kcat/Km for the p-Nitrophenyl-β-D-glucopyranoside (pNPG) as the substrate were 1063.89 U/mg, 0.36 mM, 1208.31 U/mg and 3871.92/s, respectively. Furthermore, PgBgl1 demonstrated remarkable stimulation of monosaccharides such as glucose, xylose, and galactose, as well as NaCl. PgBgl1 also demonstrated a high capacity to convert the primary soybean isoflavone glycosides (daidzin, genistin, and glycitin) into their respective aglycones. Overall, PgBgl1 exhibited high catalytic activity towards aryl glycosides, suggesting promising application prospects in the food, animal feed, and pharmaceutical industries.
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Affiliation(s)
- Jinjian He
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
- College of Horticulture and Landscape, Tianjin Agricultural University, Tianjin, 300392, China
| | - Jiajing Duan
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Pinglian Yu
- Key Laboratory of Yunnan University for Plateau Characteristic Functional Food, School of Chemistry and Chemical Engineering, Zhaotong University, Zhaotong,657000, China
| | - Yuying Li
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
| | - Mansheng Wang
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
| | - Xiu Zhang
- Ningxia Key Laboratory for the Development and Application of Microbial Resources in Extreme Environments, College of Biological Science and Engineering, North Minzu University, Yinchuan, 750021, China
| | - Zishu Chen
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
| | - Pengjun Shi
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, China
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Yao Q, Xu J, Tang N, Chen W, Gu Q, Li H. Screening, cloning, immobilization and application prospects of a novel β-glucosidase from the soil metagenome. ENVIRONMENTAL RESEARCH 2024; 244:117676. [PMID: 37996002 DOI: 10.1016/j.envres.2023.117676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/11/2023] [Accepted: 11/13/2023] [Indexed: 11/25/2023]
Abstract
The soil environment for straw return is a rich and valuable library containing many microorganisms and proteins. In this study, we aimed to screen a high-quality β-glucosidase (BGL) from the soil metagenomic library and to overcome the limitation of the low extraction rate of resveratrol in Polygonum cuspidatum. This includes the construction of a soil metagenomic library, screening of BGL, bioinformatics analysis, cloning, expression, immobilization, enzymatic property analysis, and application for the transformation of polydatin. The results showed that the soil metagenomic library of straw return was successfully constructed, and a novel BGL was screened. The identified 1356 bp long BGL belonged to the glycoside hydrolase 1 (GH1) family and was named Bgl1356. After successful cloning and expression of Bgl1356, it was immobilized using chitosan. The optimum temperature of immobilized Bgl1356 was 50 °C, and the pH was 5. It exhibited good tolerance for various metal ions (CO2+, Ni2+, Cu2+, Mn2+, Na2+, Ca2+, and Ag+) and organic solvents (DMSO, Triton-X-10, and ethanol). Enzymatic kinetics assays showed that Bgl1356 had good affinity for the substrate, and the specific enzyme activity was 234.03 U/mg. The conversion rate of polydatin by immobilized Bgl1356 was 95.70 ± 1.08%, facilitating the production of high amounts of resveratrol. Thus, this paper reports a novel temperature-, organic solvent-, and metal ion-tolerant BGL that has good application prospects in the pharmaceutical industry.
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Affiliation(s)
- Qian Yao
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China; Guangdong Key Laboratory of Bioactive Drug Research, Guangzhou, 510006, China.
| | - Jin Xu
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China; Guangdong Key Laboratory of Bioactive Drug Research, Guangzhou, 510006, China.
| | - Nan Tang
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China.
| | - Weiji Chen
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China.
| | - Quliang Gu
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China.
| | - He Li
- School of Basic Medical Sciences, Guangdong Pharmaceutical University, Guangzhou, 510006, China; Guangdong Key Laboratory of Bioactive Drug Research, Guangzhou, 510006, China.
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Nam KH. The Conformational Change of the L3 Loop Affects the Structural Changes in the Substrate Binding Pocket Entrance of β-Glucosidase. Molecules 2023; 28:7807. [PMID: 38067537 PMCID: PMC10707726 DOI: 10.3390/molecules28237807] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/20/2023] [Accepted: 11/25/2023] [Indexed: 12/18/2023] Open
Abstract
β-glucosidase (Bgl) hydrolyzes cellobiose to glucose, thereby releasing non-reducing terminal glucosyl residues. Bgl is an essential enzyme belonging to the biomass-degrading enzyme family, which plays a vital role in enzymatic saccharification during biofuel production. The four loops above the Bgl substrate-binding pocket undergo a conformational change upon substrate recognition. However, the structural dynamism of this loop and how it is conserved among Bgl family members remain unknown. Herein, to better understand the four loops above the substrate-binding pocket of Bgl, four Bgl crystal structures in Thermoanaerobacterium saccharolyticum (TsaBgl) were determined at 1.5-2.1 Å. The L1, L2, and L4 loops of TsaBgl showed a rigid conformation stabilized by their neighboring residues via hydrogen bonds and hydrophobic interactions. The TsaBgl L3 loop showed relatively high flexibility and two different N-terminal region conformations. The conformational change in the TsaBgl L3 loop induced a change in charge and shaped at the substrate-binding pocket entrance. The amino acid sequences and structures of the TsaBgl L1-4 loops were compared with other 45 Bgl proteins, and a diversity of the L2 and L3 loops was observed. Differences in amino acids and lengths of Bgls L2-L3 loop induced differences in the conformation and structure of the Bgls substrate-binding pocket entrance. These findings expand our knowledge on the molecular function of the loops in the Bgl enzyme family.
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Affiliation(s)
- Ki Hyun Nam
- College of General Education, Kookmin University, Seoul 02707, Republic of Korea
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