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Dong YQ, Shen JD, Pan L, Huang JH, Liu ZQ, Zheng YG. Mining and Characterization of Thermophilic Glucose Isomerase Based on Virtual Probe Technology. Appl Biochem Biotechnol 2023:10.1007/s12010-023-04349-5. [PMID: 36696038 DOI: 10.1007/s12010-023-04349-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2023] [Indexed: 01/26/2023]
Abstract
Fructose, which is produced by the isomerization of glucose isomerase, is a crucial precursor for the biosynthesis of rare sugars. In this study, thermophilic glucose isomerases (GI) from Caldicellulosiruptor acetigenus (CAGI), Thermoanaerobacter thermocopriae (TTGI), and Thermotoga petrophila (TPGI) were screened from GenBank database by a virtual probe and were successfully expressed in Escherichia coli BL21(DE3). The results of characterization demonstrated that the optimal pH for CAGI and TTGI were 8.0 and were maintained at 80% in a slightly acidic environment. The relative residual activities of CAGI and TTGI were found to be 40.6% and 52.6%, respectively, following an incubation period of 24 h at 90 ℃. Furthermore, CAGI and TTGI exhibited superior catalytic performance that their reaction equilibrium both reached only after an hour at 85 ℃ with 200 g/L glucose, and the highest conversion rates were 54.2% and 54.1%, respectively. This study identifies competitive enzyme candidates for fructose production in the industry with appreciable cost reduction.
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Affiliation(s)
- Yu-Qi Dong
- School of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Ji-Dong Shen
- The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Long Pan
- School of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Ji-Hong Huang
- School of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China. .,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China.
| | - Zhi-Qiang Liu
- The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China.
| | - Yu-Guo Zheng
- The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
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Miyamoto RY, de Melo RR, de Mesquita Sampaio IL, de Sousa AS, Morais ER, Sargo CR, Zanphorlin LM. Paradigm shift in xylose isomerase usage: a novel scenario with distinct applications. Crit Rev Biotechnol 2021; 42:693-712. [PMID: 34641740 DOI: 10.1080/07388551.2021.1962241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Isomerases are enzymes that induce physical changes in a molecule without affecting the original molecular formula. Among this class of enzymes, xylose isomerases (XIs) are the most studied to date, partly due to their extensive application in industrial processes to produce high-fructose corn sirups. In recent years, the need for sustainable initiatives has triggered efforts to improve the biobased economy through the use of renewable raw materials. In this context, D-xylose usage is crucial as it is the second-most abundant sugar in nature. The application of XIs in biotransforming xylose, enabling downstream metabolism in several microorganisms, is a smart strategy for ensuring a low-carbon footprint and producing several value-added biochemicals with broad industrial applications such as in the food, cosmetics, pharmaceutical, and polymer industries. Considering recent advancements that have expanded the range of applications of XIs, this review provides a comprehensive and concise overview of XIs, from their primary sources to the biochemical and structural features that influence their mechanisms of action. This comprehensive review may help address the challenges involved in XI applications in different industries and facilitate the exploitation of xylose bioprocesses.
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Affiliation(s)
- Renan Yuji Miyamoto
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil.,Faculty of Pharmaceutical Sciences (FCF), State University of Campinas (UNICAMP), Campinas, Brazil
| | - Ricardo Rodrigues de Melo
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Isabelle Lobo de Mesquita Sampaio
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil.,Faculty of Food Engineering (FEA), State University of Campinas (UNICAMP), Campinas, Brazil
| | - Amanda Silva de Sousa
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Edvaldo Rodrigo Morais
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil.,Faculty of Food Engineering (FEA), State University of Campinas (UNICAMP), Campinas, Brazil
| | - Cintia Regina Sargo
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Leticia Maria Zanphorlin
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
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Zhao J, Wei H, Chen J, Li L, Li K, Liu J. Efficient biosynthesis of D-allulose in Bacillus subtilis through D-psicose 3-epimerase translation modification. Int J Biol Macromol 2021; 187:1-8. [PMID: 34293357 DOI: 10.1016/j.ijbiomac.2021.07.093] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/01/2021] [Accepted: 07/14/2021] [Indexed: 10/20/2022]
Abstract
The combined catalysis of glucose isomerase (GI) and D-psicose 3-epimerase (DPEase) provided a convenient route for the direct synthesis of D-allulose from d-glucose, whose cost is lower than d-fructose. In the present research, the weak activity of DPEase was the key rate-limiting step and resulted in the accumulation of d-fructose in engineered Bacillus subtilis. Then, the 5'-untranslated region (5'-UTR) structure of the mRNA translational initiation region was optimized for the precise control of DPEase expression. The manipulation of the 5'-UTR region promoted the accessibility to ribosome binding and the stability of mRNA, resulting in a maximum of 1.73- and 1.98-fold increase in DPEase activity and intracellular mRNA amount, respectively. Under the optimal catalytic conditions of 75 °C, pH 6.5, 110 g/L d-glucose, and 1 mmol/L Co2+, the reaction equilibrium time was reduced from 7.6 h to 6.1 h. We hope that our results could provide a facilitated strategy for large-scale production of D-allulose at low-cost.
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Affiliation(s)
- Jingyi Zhao
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
| | - Hongbei Wei
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
| | - Jing Chen
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
| | - Lihong Li
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
| | - Kai Li
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China; Sugar Industry Collaborative Innovation Center, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
| | - Jidong Liu
- College of Light Industry and Food Engineering, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China; Sugar Industry Collaborative Innovation Center, Guangxi University, 100 Daxue Road, Nanning 530004, Guangxi, China.
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Mehrabi P, Schulz EC, Agthe M, Horrell S, Bourenkov G, von Stetten D, Leimkohl JP, Schikora H, Schneider TR, Pearson AR, Tellkamp F, Miller RJD. Liquid application method for time-resolved analyses by serial synchrotron crystallography. Nat Methods 2019; 16:979-982. [DOI: 10.1038/s41592-019-0553-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 08/06/2019] [Indexed: 01/01/2023]
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Parageobacillus thermantarcticus, an Antarctic Cell Factory: From Crop Residue Valorization by Green Chemistry to Astrobiology Studies. DIVERSITY 2019. [DOI: 10.3390/d11080128] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Knowledge of Antarctic habitat biodiversity, both marine and terrestrial, has increased considerably in recent years, causing considerable development in the studies of life science related to Antarctica. In the Austral summer 1986–1987, a new thermophilic bacterium, Parageobacillus thermantarcticus strain M1 was isolated from geothermal soil of the crater of Mount Melbourne (74°22′ S, 164°40′ E) during the Italian Antarctic Expedition. In addition to the biotechnological potential due to the production of exopolysaccharides and thermostable enzymes, successful studies have demonstrated its use in the green chemistry for the transformation and valorization of residual biomass and its employment as a suitable microbial model for astrobiology studies. The recent acquisition of its genome sequence opens up new opportunities for the use of this versatile bacterium in still unexplored biotechnology sectors.
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A novel thermostable and efficient Class II glucose isomerase from the thermophilic Caldicoprobacter algeriensis: Biochemical characterization, molecular investigation, and application in High Fructose Syrup production. Int J Biol Macromol 2019; 129:31-40. [DOI: 10.1016/j.ijbiomac.2019.01.150] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 01/18/2019] [Accepted: 01/26/2019] [Indexed: 01/01/2023]
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Konak L, Kolcuoğlu Y, Ozbek E, Colak A, Ergenoglu B. Purification and characterization of an extremely stable glucose isomerase from Geobacillus thermodenitrificans TH2. APPL BIOCHEM MICRO+ 2013. [DOI: 10.1134/s0003683814010062] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Karaoglu H, Yanmis D, Sal FA, Celik A, Canakci S, Belduz AO. Biochemical characterization of a novel glucose isomerase from Anoxybacillus gonensis G2T that displays a high level of activity and thermal stability. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.molcatb.2013.08.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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D'haeseleer P, Gladden JM, Allgaier M, Chain PSG, Tringe SG, Malfatti SA, Aldrich JT, Nicora CD, Robinson EW, Paša-Tolić L, Hugenholtz P, Simmons BA, Singer SW. Proteogenomic analysis of a thermophilic bacterial consortium adapted to deconstruct switchgrass. PLoS One 2013; 8:e68465. [PMID: 23894306 PMCID: PMC3716776 DOI: 10.1371/journal.pone.0068465] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 05/29/2013] [Indexed: 12/02/2022] Open
Abstract
Thermophilic bacteria are a potential source of enzymes for the deconstruction of lignocellulosic biomass. However, the complement of proteins used to deconstruct biomass and the specific roles of different microbial groups in thermophilic biomass deconstruction are not well-explored. Here we report on the metagenomic and proteogenomic analyses of a compost-derived bacterial consortium adapted to switchgrass at elevated temperature with high levels of glycoside hydrolase activities. Near-complete genomes were reconstructed for the most abundant populations, which included composite genomes for populations closely related to sequenced strains of Thermus thermophilus and Rhodothermus marinus, and for novel populations that are related to thermophilic Paenibacilli and an uncultivated subdivision of the little-studied Gemmatimonadetes phylum. Partial genomes were also reconstructed for a number of lower abundance thermophilic Chloroflexi populations. Identification of genes for lignocellulose processing and metabolic reconstructions suggested Rhodothermus, Paenibacillus and Gemmatimonadetes as key groups for deconstructing biomass, and Thermus as a group that may primarily metabolize low molecular weight compounds. Mass spectrometry-based proteomic analysis of the consortium was used to identify >3000 proteins in fractionated samples from the cultures, and confirmed the importance of Paenibacillus and Gemmatimonadetes to biomass deconstruction. These studies also indicate that there are unexplored proteins with important roles in bacterial lignocellulose deconstruction.
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Affiliation(s)
- Patrik D'haeseleer
- Joint BioEnergy Institute, Emeryville, California, United States of America.
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Ben Hlima H, Aghajari N, Ben Ali M, Haser R, Bejar S. Engineered glucose isomerase from Streptomyces sp. SK is resistant to Ca2+ inhibition and Co2+ independent. ACTA ACUST UNITED AC 2012; 39:537-46. [DOI: 10.1007/s10295-011-1061-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 11/08/2011] [Indexed: 11/24/2022]
Abstract
Abstract
The role of two amino acid residues linked to the two catalytic histidines His54 and His220 in kinetics and physicochemical properties of the Streptomyces sp. SK glucose isomerase (SKGI) was investigated by site-directed mutagenesis and molecular modeling. Two single mutations, F53L and G219D, and a double mutation F53L/G219D was introduced into the xylA SKGI gene. The F53L mutation increases the thermostability and the catalytic efficiency and also slightly shifts the optimum pH from 6.5 to 7, but displays a profile being similar to that of the wild-type enzyme concerning the effect of various metal ions. The G219D mutant is resistant to calcium inhibition retaining about 80% of its residual activity in 10 mM Ca2+ instead of 10% for the wild-type. This variant is activated by Mn2+ ions, but not Co2+, as seen for the wild-type enzyme. It does not require the latter for its thermostability, but has its half-life time displaced from 50 to 20 min at 85°C. The double mutation F53L/G219D restores the thermostability as seen for the wild-type enzyme while maintaining the resistance to the calcium inhibition. Molecular modeling suggests that the increase in thermostability is due to new hydrophobic interactions stabilizing α2 helix and that the resistance to calcium inhibition is a result of narrowing the binding site of catalytic ion.
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Affiliation(s)
- Hajer Ben Hlima
- grid.412124.0 0000000123235644 Laboratoire de Microorganismes et de Biomolécules, Centre de Biotechnologie de Sfax Université de Sfax B.P 1177 Route de Sidi Mansour Km 6 3018 Sfax Tunisia
| | - Nushin Aghajari
- grid.25697.3f 0000 0001 2172 4233 Laboratoire de BioCristallographie et Biologie Structurale des Cibles Thérapeutiques, Bases Moléculaires et Structurales des Systèmes Infectieux UMR 5086–CNRS/Université Lyon 1, Institut de Biologie et Chimie des Protéines FR3302, 7 Passage du Vercors 69367 Lyon cedex 07 France
| | - Mamdouh Ben Ali
- grid.412124.0 0000000123235644 Laboratoire de Microorganismes et de Biomolécules, Centre de Biotechnologie de Sfax Université de Sfax B.P 1177 Route de Sidi Mansour Km 6 3018 Sfax Tunisia
| | - Richard Haser
- grid.25697.3f 0000 0001 2172 4233 Laboratoire de BioCristallographie et Biologie Structurale des Cibles Thérapeutiques, Bases Moléculaires et Structurales des Systèmes Infectieux UMR 5086–CNRS/Université Lyon 1, Institut de Biologie et Chimie des Protéines FR3302, 7 Passage du Vercors 69367 Lyon cedex 07 France
| | - Samir Bejar
- grid.412124.0 0000000123235644 Laboratoire de Microorganismes et de Biomolécules, Centre de Biotechnologie de Sfax Université de Sfax B.P 1177 Route de Sidi Mansour Km 6 3018 Sfax Tunisia
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Fan L, Zhang Y, Qu W, Wang J, Shao W. Cloning and analysis of the xylAB operon and characterization of xylose isomerase from Thermoanaerobacter ethanolicus. Biotechnol Lett 2010; 33:593-8. [PMID: 21072563 DOI: 10.1007/s10529-010-0463-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 10/27/2010] [Indexed: 10/18/2022]
Abstract
Three genes, xylA-like, xylA and xylB, were cloned and sequenced from the chromosome of Thermoanaerobacter ethanolicus JW200. xylA and xylB share an operon and encode xylose isomerase and xylulokinase, respectively. The xylA-like gene locates upstream of xylAB operon and encodes a hypothetical protein that lacks xylose isomerase activity. The xylose isomerase was expressed in Escherichia coli and purified by heat treatment and an ion-exchange chromatography. The enzyme had highest activity at 85°C and pH 7.0, and a half-life for 1 h at 85°C. The K (m) and V (max) values for xylose were 11 mM and 25 U/mg, respectively. The high level of expression, easy purification, and thermostability of the XylA from T. ethanolicus JW200 suggests industrial usefulness.
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Affiliation(s)
- Lijuan Fan
- Jiangsu Key Laboratory for Biodiversity and Bio-resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210046, China
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Çalık P, Angardi V, Haykır NI, Boyacı IH. Glucose isomerase production on a xylan-based medium by Bacillus thermoantarcticus. Biochem Eng J 2009. [DOI: 10.1016/j.bej.2008.08.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Tao H, Gonzalez R, Martinez A, Rodriguez M, Ingram LO, Preston JF, Shanmugam KT. Engineering a homo-ethanol pathway in Escherichia coli: increased glycolytic flux and levels of expression of glycolytic genes during xylose fermentation. J Bacteriol 2001; 183:2979-88. [PMID: 11325924 PMCID: PMC95196 DOI: 10.1128/jb.183.10.2979-2988.2001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Replacement of the native fermentation pathway in Escherichia coli B with a homo-ethanol pathway from Zymomonas mobilis (pdc and adhB genes) resulted in a 30 to 50% increase in growth rate and glycolytic flux during the anaerobic fermentation of xylose. Gene array analysis was used as a tool to investigate differences in expression levels for the 30 genes involved in xylose catabolism in the parent (strain B) and the engineered strain (KO11). Of the 4,290 total open reading frames, only 8% were expressed at a significantly higher level in KO11 (P < 0.05). In contrast, over half of the 30 genes involved in the catabolism of xylose to pyruvate were expressed at 1.5-fold- to 8-fold-higher levels in KO11. For 14 of the 30 genes, higher expression was statistically significant at the 95% confidence level (xylAB, xylE, xylFG, xylR, rpiA, rpiB, pfkA, fbaA, tpiA, gapA, pgk, and pykA) during active fermentation (6, 12, and 24 h). Values at single time points for only four of these genes (eno, fbaA, fbaB, and talA) were higher in strain B than in KO11. The relationship between changes in mRNA (cDNA) levels and changes in specific activities was verified for two genes (xylA and xylB) with good agreement. In KO11, expression levels and activities were threefold higher than in strain B for xylose isomerase (xylA) and twofold higher for xylulokinase (xylB). Increased expression of genes involved in xylose catabolism is proposed as the basis for the increase in growth rate and glycolytic flux in ethanologenic KO11.
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Affiliation(s)
- H Tao
- Institute of Food and Agricultural Sciences, Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
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Raykovska V, Dolashka-Angelova P, Paskaleva D, Stoeva S, Abashev J, Kirkov L, Voelter W. Isolation and characterization of a xylose-glucose isomerase from a new strain Streptomyces thermovulgaris 127, var. 7-86. Biochem Cell Biol 2001. [DOI: 10.1139/o00-100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A thermostable D-xyloseglucose isomerase was isolated from the thermophilic strain Streptomyces thermovulgaris 127, var. 7-86, as a result of mutagenic treatment by γ-irradiation of the parent strain, by precipitation and sequential chromatographies on DEAESephadex A50, TSK-gel, FPLC-Mono Q/HR, and Superose 12 columns. The N-terminal amino acid sequence and amino acid analysis shows 7392% homology with xyloseglucose isomerases from other sources. The native molecular mass, determined by gel filtration on a Superose 12 column, is 180 kDa, and 44.6 and 45 kDa were calculated, based on amino acid analysis and 10% SDS-PAGE, respectively. Both, the activity and stability of the enzyme were investigated toward pH, temperature, and denaturation with guanidine hydrochloride. The enzyme activity showed a clear pH optimum between pH 7.2 and 9.0 with D-glucose and 7.4 and 8.3 with D-xylose as substrates, respectively. The enzyme is active up to 6085°C at pH 7.0, using D-glucose, and up to 5060°C at pH 7.6, using D-xylose as substrates. The activation energy (Ea = 46 kJ·mol1) and the critical temperature (Tc = 60°C) were determined by fluorescence spectroscopy. Tc is in close coincidence with the melting temperature of denaturation (Tm = 59°C), determined by circular dichroism (CD) spectroscopy. The free energy of stabilization in water after denaturation with Gdn.HCl was calculated to be 12 kJ·mol1. The specific activity (km values) for D-xylose-glucose isomerase at 70°C toward different substrates, D-xylose, D-glucose, and D-ribose, were determined to be 4.4, 55.5, and 13.3 mM, recpectively.Key words: D-xylose-glucose isomerase, protein sequencing, protein stability, protein denaturation.
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Abstract
Glucose isomerase (GI) (D-xylose ketol-isomerase; EC. 5.3.1.5) catalyzes the reversible isomerization of D-glucose and D-xylose to D-fructose and D-xylulose, respectively. The enzyme has the largest market in the food industry because of its application in the production of high-fructose corn syrup (HFCS). HFCS, an equilibrium mixture of glucose and fructose, is 1.3 times sweeter than sucrose and serves as a sweetener for use by diabetics. Interconversion of xylose to xylulose by GI serves a nutritional requirement in saprophytic bacteria and has a potential application in the bioconversion of hemicellulose to ethanol. The enzyme is widely distributed in prokaryotes. Intensive research efforts are directed toward improving its suitability for industrial application. Development of microbial strains capable of utilizing xylan-containing raw materials for growth or screening for constitutive mutants of GI is expected to lead to discontinuation of the use of xylose as an inducer for the production of the enzyme. Elimination of Co2+ from the fermentation medium is desirable for avoiding health problems arising from human consumption of HFCS. Immobilization of GI provides an efficient means for its easy recovery and reuse and lowers the cost of its use. X-ray crystallographic and genetic engineering studies support a hydride shift mechanism for the action of GI. Cloning of GI in homologous as well as heterologous hosts has been carried out, with the prime aim of overproducing the enzyme and deciphering the genetic organization of individual genes (xylA, xylB, and xylR) in the xyl operon of different microorganisms. The organization of xylA and xylB seems to be highly conserved in all bacteria. The two genes are transcribed from the same strand in Escherichia coli and Bacillus and Lactobacillus species, whereas they are transcribed divergently on different strands in Streptomyces species. A comparison of the xylA sequences from several bacterial sources revealed the presence of two signature sequences, VXW(GP)GREG(YSTAE)E and (LIVM)EPKPX(EQ)P. The use of an inexpensive inducer in the fermentation medium devoid of Co2+ and redesigning of a tailor-made GI with increased thermostability, higher affinity for glucose, and lower pH optimum will contribute significantly to the development of an economically feasible commercial process for enzymatic isomerization of glucose to fructose. Manipulation of the GI gene by site-directed mutagenesis holds promise that a GI suitable for biotechnological applications will be produced in the foreseeable future.
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Affiliation(s)
- S H Bhosale
- Division of Biochemical Sciences, National Chemical Laboratory, Pune, India
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Abstract
Glucose isomerase (GI) (D-xylose ketol-isomerase; EC. 5.3.1.5) catalyzes the reversible isomerization of D-glucose and D-xylose to D-fructose and D-xylulose, respectively. The enzyme has the largest market in the food industry because of its application in the production of high-fructose corn syrup (HFCS). HFCS, an equilibrium mixture of glucose and fructose, is 1.3 times sweeter than sucrose and serves as a sweetener for use by diabetics. Interconversion of xylose to xylulose by GI serves a nutritional requirement in saprophytic bacteria and has a potential application in the bioconversion of hemicellulose to ethanol. The enzyme is widely distributed in prokaryotes. Intensive research efforts are directed toward improving its suitability for industrial application. Development of microbial strains capable of utilizing xylan-containing raw materials for growth or screening for constitutive mutants of GI is expected to lead to discontinuation of the use of xylose as an inducer for the production of the enzyme. Elimination of Co2+ from the fermentation medium is desirable for avoiding health problems arising from human consumption of HFCS. Immobilization of GI provides an efficient means for its easy recovery and reuse and lowers the cost of its use. X-ray crystallographic and genetic engineering studies support a hydride shift mechanism for the action of GI. Cloning of GI in homologous as well as heterologous hosts has been carried out, with the prime aim of overproducing the enzyme and deciphering the genetic organization of individual genes (xylA, xylB, and xylR) in the xyl operon of different microorganisms. The organization of xylA and xylB seems to be highly conserved in all bacteria. The two genes are transcribed from the same strand in Escherichia coli and Bacillus and Lactobacillus species, whereas they are transcribed divergently on different strands in Streptomyces species. A comparison of the xylA sequences from several bacterial sources revealed the presence of two signature sequences, VXW(GP)GREG(YSTAE)E and (LIVM)EPKPX(EQ)P. The use of an inexpensive inducer in the fermentation medium devoid of Co2+ and redesigning of a tailor-made GI with increased thermostability, higher affinity for glucose, and lower pH optimum will contribute significantly to the development of an economically feasible commercial process for enzymatic isomerization of glucose to fructose. Manipulation of the GI gene by site-directed mutagenesis holds promise that a GI suitable for biotechnological applications will be produced in the foreseeable future.
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Affiliation(s)
- S H Bhosale
- Division of Biochemical Sciences, National Chemical Laboratory, Pune, India
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