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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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2
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Vassão DG, Wielsch N, Gomes AMDMM, Gebauer-Jung S, Hupfer Y, Svatoš A, Gershenzon J. Plant Defensive β-Glucosidases Resist Digestion and Sustain Activity in the Gut of a Lepidopteran Herbivore. FRONTIERS IN PLANT SCIENCE 2018; 9:1389. [PMID: 30349548 PMCID: PMC6186830 DOI: 10.3389/fpls.2018.01389] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/31/2018] [Indexed: 05/07/2023]
Abstract
Two-component activated chemical defenses are a major part of many plants' strategies to disrupt herbivory. The activation step is often the β-glucosidase-catalyzed removal of a glucose moiety from a pro-toxin, leading to an unstable and toxic aglycone. While some β-glucosidases have been well studied, several aspects of their roles in vivo, such as their precise sites of enzymatic activity during and after ingestion, and the importance of particular isoforms in plant defense are still not fully understood. Here, plant defensive β-glucosidases from maize, white mustard and almonds were shown to resist digestion by larvae of the generalist lepidopteran Spodoptera littoralis, and the majority of the ingested activities toward both general and plant pro-toxic substrates was recovered in the frass. Among other proteins potentially involved in defense, we identified specific plant β-glucosidases and a maize β-glucosidase aggregating factor in frass from plant-fed insects using proteomic methods. We therefore found that, while S. littoralis larvae efficiently degraded bulk food protein during digestion, β-glucosidases were among a small number of plant defensive proteins that resist insect digestive proteolysis. These enzymes remain intact in the gut lumen and frass and can therefore further catalyze the activation of plant defenses after ingestion, especially in pH-neutral regions of the digestive system. As most of the ingested enzymatic activity persists in the frass, and only particular β-glucosidases were detected via proteomic analyses, our data support the involvement of specific isoforms (maize ZmGlu1 and S. alba MA1 myrosinase) in defense in vivo.
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Affiliation(s)
| | - Natalie Wielsch
- Research Group Mass Spectrometry/Proteomics, Max Planck Institute for Chemical Ecology, Jena, Germany
| | | | - Steffi Gebauer-Jung
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Yvonne Hupfer
- Research Group Mass Spectrometry/Proteomics, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Aleš Svatoš
- Research Group Mass Spectrometry/Proteomics, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Jonathan Gershenzon
- Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany
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3
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Klimeš P, Mazura P, Turek D, Brzobohatý B. An automated method to evaluate the enzyme kinetics of β-glucosidases. Protein Sci 2016; 26:382-388. [PMID: 27862518 DOI: 10.1002/pro.3078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 10/27/2016] [Accepted: 11/02/2016] [Indexed: 11/05/2022]
Abstract
Enzyme kinetic measurements are important for the characterization and engineering of biocatalysts, with applications in a wide range of research fields. The measurement of initial reaction velocity is usually slow and laborious, which motivated us to explore the possibilities for automating this process. Our model enzyme is the maize β-glucosidase Zm-p60.1. Zm-p60.1 plays a significant role in plant growth and development by regulating levels of the active plant hormone cytokinin. Zm-p60.1 belongs to a wide group of hydrolytic enzymes. Members of this group hydrolyze several different types of glucosides, releasing glucose as a secondary product. Enzyme kinetic measurements using artificial substrates are well established, but burdensome and time-consuming. Thus, they are a suitable target for process automation. Simple optical methods for enzyme kinetic measurements using natural substrates are often impossible given the optical properties of the enzymatic reaction products. However, we have developed an automated method based on glucose detection, as glucose is released from all substrates of glucosidase reactions. The presented method can obtain 24 data points from up to 15 substrate concentrations to precisely describe the enzyme kinetics. The combination of an automated liquid handling process with assays that have been optimized for measuring the initial hydrolysis velocity of β-glucosidases yields two distinct methods that are faster, cheaper, and more accurate than the established protocols.
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Affiliation(s)
- Pavel Klimeš
- Department of Molecular Biology and Radiobiology, Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR, v.v.i. and CEITEC-Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, Brno, CZ-613 00, Czech Republic
| | - Pavel Mazura
- Department of Molecular Biology and Radiobiology, Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR, v.v.i. and CEITEC-Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, Brno, CZ-613 00, Czech Republic
| | - Dušan Turek
- Department of Molecular Biology and Radiobiology, Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR, v.v.i. and CEITEC-Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, Brno, CZ-613 00, Czech Republic
| | - Břetislav Brzobohatý
- Department of Molecular Biology and Radiobiology, Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR, v.v.i. and CEITEC-Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, Brno, CZ-613 00, Czech Republic
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4
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An intermolecular disulfide bond is required for thermostability and thermoactivity of β-glycosidase from Thermococcus kodakarensis KOD1. Appl Microbiol Biotechnol 2014; 98:7825-36. [PMID: 24728717 DOI: 10.1007/s00253-014-5731-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 03/26/2014] [Accepted: 03/27/2014] [Indexed: 12/24/2022]
Abstract
Scientists are interested in understanding the molecular origin of protein thermostability and thermoactivity for possible biotechnological applications. The enzymes from extremophilic organisms have been of particular interest in the last two decades. β-glycosidase, Tkβgly is a hyperthermophilic enzyme from Thermococcus kodakarensis KOD1. Tkβgly contains two conserved cysteine residues, C88 and C376. The protein tertiary structure obtained through homology modeling suggests that the C88 residue is located on the surface whereas C376 is inside the protein. To study the role of these cysteine residues, we substituted C88 and C376 with serine residues through site-directed mutagenesis. The wild-type and C376S protein existed in dimeric form and C88S in monomeric form, in an SDS-PAGE gel under non-reducing conditions. Optimal temperature experiments revealed that the wild-type was active at 100 °C whereas the C88S mutant exhibited optimal activity at 70 °C. The half-life of the enzyme at 70 °C was drastically reduced from 266 h to less than 1 h. Although C88 was not present in the active site region, the kcat/Km of C88S was reduced by 2-fold. Based on the structural model and biochemical properties, we propose that C88 is crucial in maintaining the thermostability and thermoactivity of the Tkβgly enzyme.
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Sansenya S, Opassiri R, Kuaprasert B, Chen CJ, Ketudat Cairns JR. The crystal structure of rice (Oryza sativa L.) Os4BGlu12, an oligosaccharide and tuberonic acid glucoside-hydrolyzing β-glucosidase with significant thioglucohydrolase activity. Arch Biochem Biophys 2011; 510:62-72. [DOI: 10.1016/j.abb.2011.04.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 04/08/2011] [Accepted: 04/10/2011] [Indexed: 11/17/2022]
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Focused directed evolution of β-glucosidases: theoretical versus real effectiveness of a minimal working setup and simple robust screening. Carbohydr Res 2011; 346:238-42. [DOI: 10.1016/j.carres.2010.08.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 08/22/2010] [Indexed: 11/19/2022]
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Dopitová R, Mazura P, Janda L, Chaloupková R, Jeřábek P, Damborský J, Filipi T, Kiran NS, Brzobohatý B. Functional analysis of the aglycone-binding site of the maize β-glucosidase Zm-p60.1. FEBS J 2008; 275:6123-35. [DOI: 10.1111/j.1742-4658.2008.06735.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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8
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Gupta N, Ragsdale SW. Dual roles of an essential cysteine residue in activity of a redox-regulated bacterial transcriptional activator. J Biol Chem 2008; 283:28721-8. [PMID: 18687692 DOI: 10.1074/jbc.m800630200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CprK from Desulfitobacterium dehalogenans is the first characterized transcriptional regulator of anaerobic dehalorespiration and is controlled at two levels: redox and effector binding. In the reduced state and in the presence of chlorinated aromatic compounds, CprK positively regulates expression of the cpr gene cluster. One of the products of the cpr gene cluster is CprA, which catalyzes the reductive dehalogenation of chlorinated aromatic compounds. Redox regulation of CprK occurs through a thiol/disulfide redox switch, which includes two classes of cysteine residues. Under oxidizing conditions, Cys11 and Cys200 form an intermolecular disulfide bond, whereas Cys105 and Cys111 form an intramolecular disulfide. Here, we report that Cys11 is involved in redox inactivation in vivo. Upon replacement of Cys11 with serine, alanine, or aspartate, CprK loses its DNA binding activity. C11A is unstable; however, circular dichroism studies demonstrate that the stability and overall secondary structures of CprK and the C11S and C11D variants are similar. Furthermore, effector binding remains intact in the C11S and C11D variants. However, fluorescence spectroscopic results reveal that the tertiary structures of the C11S and C11D variants differ from that of the wild type protein. Thus, Cys11 plays a dual role as a redox switch and in maintaining the correct tertiary structure that promotes DNA binding.
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Affiliation(s)
- Nirupama Gupta
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Mighigan 48109-0606, USA
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9
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Morant AV, Jørgensen K, Jørgensen C, Paquette SM, Sánchez-Pérez R, Møller BL, Bak S. beta-Glucosidases as detonators of plant chemical defense. PHYTOCHEMISTRY 2008; 69:1795-813. [PMID: 18472115 DOI: 10.1016/j.phytochem.2008.03.006] [Citation(s) in RCA: 308] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 03/06/2008] [Indexed: 05/03/2023]
Abstract
Some plant secondary metabolites are classified as phytoanticipins. When plant tissue in which they are present is disrupted, the phytoanticipins are bio-activated by the action of beta-glucosidases. These binary systems--two sets of components that when separated are relatively inert--provide plants with an immediate chemical defense against protruding herbivores and pathogens. This review provides an update on our knowledge of the beta-glucosidases involved in activation of the four major classes of phytoanticipins: cyanogenic glucosides, benzoxazinoid glucosides, avenacosides and glucosinolates. New aspects of the role of specific proteins that either control oligomerization of the beta-glucosidases or modulate their product specificity are discussed in an evolutionary perspective.
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Affiliation(s)
- Anne Vinther Morant
- Plant Biochemistry Laboratory, Department of Plant Biology and The VKR Research Centre Proactive Plants, University of Copenhagen, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark
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10
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Egido-Gabás M, Canals D, Casas J, Llebaria A, Delgado A. Aminocyclitols as Pharmacological Chaperones for Glucocerebrosidase, a Defective Enzyme in Gaucher Disease. ChemMedChem 2007; 2:992-4. [PMID: 17479993 DOI: 10.1002/cmdc.200700061] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Meritxell Egido-Gabás
- Research Unit on Bioactive Molecules, Departament de Química Orgànica Biològica, Institut d'Investigacions Químiques i Ambientals de Barcelona (C.S.I.C), Jordi Girona 18-26, 08034 Barcelona, Spain
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11
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Mazura P, Fohlerová R, Brzobohatý B, Kiran NS, Janda L. A new, sensitive method for enzyme kinetic studies of scarce glucosides. ACTA ACUST UNITED AC 2006; 68:55-63. [PMID: 16730803 DOI: 10.1016/j.jbbm.2006.03.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 03/28/2006] [Accepted: 03/29/2006] [Indexed: 11/26/2022]
Abstract
The maize beta-glucosidase Zm-p60.1 is important for the regulation of plant development through its role in the targeted release of free cytokinins from cytokinin-O-glucosides, their inactive storage forms. Enzyme kinetics studies using these scarce substrates close to physiological concentrations are difficult due to two reasons: (a) Available methods are mainly suited for end-point kinetics. (b) These methods are not sufficiently sensitive when using scarce glucoside substrates. We developed a glucose assay using a system comprising three enzymes beta-glucosidase, glucose oxidase and horseradish peroxidase, with the new substrate N-acetyl-3,7-dihydroxyphenoxazine-Amplex Ultra Red reagent (Molecular Probes). A calibration curve was constructed for resorufin and validation was carried out by comparing our method with the standard spectrophotometric method using p-nitrophenyl-beta-d-glucopyranoside. In comparison with the other methods, this method is more sensitive, precise and accurate. The assay is rapid and hence suited for continuous kinetics, it is readily adapted to suit automated procedures, and potential applications include its use in studying the physiological role(s) of enzymes that cleave scarce glucoside substrates.
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Affiliation(s)
- Pavel Mazura
- Department of Functional Genomics and Proteomics, Masaryk University, University Campus Bohunice, Kamenice 3, CZ-62500 Brno, Czech Republic
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12
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Dayan FE, Kuhajek JM, Canel C, Watson SB, Moraes RM. Podophyllum peltatum possesses a beta-glucosidase with high substrate specificity for the aryltetralin lignan podophyllotoxin. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1646:157-63. [PMID: 12637023 DOI: 10.1016/s1570-9639(03)00004-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A beta-glucosidase with high specificity for podophyllotoxin-4-O-beta-D-glucopyranoside was purified from the leaves of Podophyllum peltatum. The 65-kDa polypeptide had optimum activity at pH 5.0 and was essentially inactive at pH 6.5 or above. Maximum catalytic activity of this glucosidase was obtained at 45 degrees C, but the enzyme was not heat stable. This beta-glucosidase displayed higher substrate specificity for podophyllotoxin-4-O-beta-D-glucopyranoside than for the other lignans tested, and for the (1-->3) linkage of laminaribiose than for other glucosidic linkages.
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Affiliation(s)
- Franck E Dayan
- Natural Products Utilization Research Unit, Agricultural Research Service, United States Department of Agriculture, P.O. Box 8048, University, MS 38677, USA.
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13
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Hsieh MC, Graham TL. Partial purification and characterization of a soybean beta-glucosidase with high specific activity towards isoflavone conjugates. PHYTOCHEMISTRY 2001; 58:995-1005. [PMID: 11730862 DOI: 10.1016/s0031-9422(01)00380-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A beta-glucosidase with high specific activity towards isoflavone conjugates was purified from soybean [Glycine max] roots by high salt extraction from a low speed centrifugal pellet and subsequent anion and cation exchange chromatography. Purification required stabilization throughout fractionation in 10% glycerol. The enzyme is most likely a dimer (approximate M(r) 165 kDa) with potential subunits of M(r) 80 and/or 75 kDa. The pH and temperature optima are pH 6 and 30 degrees C, respectively. The enzyme was highly heat-stable. Of the various potential effectors examined, silver and mercury ions were the most inhibitory. The IC(50) of silver ions was increased from 140 microM to 14 mM in the presence of 250 microM beta-mercaptoethanol. Glucono-delta-lactone was not strongly inhibitory (IC(50) 24 mM). The activity was highly active against isoflavone conjugates, with a specificity constant 160-1000 fold higher for isoflavone conjugates over the generic chromogenic substrate, p-nitrophenyl beta-glucoside. The enzyme was inactive against the flavonol glycosides tested. The partially purified enzyme had similar K(m) and k(cat) towards 7-O-glucosyl- and 7-O-glucosyl-6"-malonyl-isoflavones, suggesting that it may be able to cleave the esterified glucosyl conjugate. We hypothesize that the enzyme is involved in the release of daidzein and genistein, both of which play central roles in soybean defense.
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Affiliation(s)
- M C Hsieh
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, USA
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Zouhar J, Vévodová J, Marek J, Damborský J, Su XD, Brzobohatý B. Insights into the functional architecture of the catalytic center of a maize beta-glucosidase Zm-p60.1. PLANT PHYSIOLOGY 2001. [PMID: 11706179 DOI: 10.1104/pp.010712] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The maize (Zea mays) beta-glucosidase Zm-p60.1 has been implicated in regulation of plant development by the targeted release of free cytokinins from cytokinin-O-glucosides, their inactive storage forms. The crystal structure of the wild-type enzyme was solved at 2.05-A resolution, allowing molecular docking analysis to be conducted. This indicated that the enzyme specificity toward substrates with aryl aglycones is determined by aglycone aromatic system stacking with W373, and interactions with edges of F193, F200, and F461 located opposite W373 in a slot-like aglycone-binding site. These aglycone-active site interactions recently were hypothesized to determine substrate specificity in inactive enzyme substrate complexes of ZM-Glu1, an allozyme of Zm-p60.1. Here, we test this hypothesis by kinetic analysis of F193I/Y/W mutants. The decreased K(m) of all mutants confirmed the involvement of F193 in determining enzyme affinity toward substrates with an aromatic aglycone. It was unexpected that a 30-fold decrease in k(cat) was found in F193I mutant compared with the wild type. Kinetic analysis and computer modeling demonstrated that the F193-aglycone-W373 interaction not only contributes to aglycone recognition as hypothesized previously but also codetermines catalytic rate by fixing the glucosidic bond in an orientation favorable for attack by the catalytic pair, E186 and E401. The catalytic pair, assigned initially by their location in the structure, was confirmed by kinetic analysis of E186D/Q and E401D/Q mutants. It was unexpected that the E401D as well as C205S and C211S mutations dramatically impaired the assembly of a catalysis-competent homodimer, suggesting novel links between the active site structure and dimer formation.
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Affiliation(s)
- J Zouhar
- Department of Functional Genomics and Proteomics, Faculty of Science, Masaryk University, Kotláská 2, CZ-61137 Brno, Czech Republic
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15
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Czjzek M, Cicek M, Zamboni V, Burmeister WP, Bevan DR, Henrissat B, Esen A. Crystal structure of a monocotyledon (maize ZMGlu1) beta-glucosidase and a model of its complex with p-nitrophenyl beta-D-thioglucoside. Biochem J 2001; 354:37-46. [PMID: 11171077 PMCID: PMC1221626 DOI: 10.1042/0264-6021:3540037] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The maize beta-glucosidase isoenzymes ZMGlu1 and ZMGlu2 hydrolyse the abundant natural substrate DIMBOAGlc (2-O-beta-D-glucopyranosyl-4-hydroxy-7-methoxy-1,4-benzoxazin-3-one), whose aglycone DIMBOA (2,4-hydroxy-7-methoxy-1,4-benzoxazin-3-one) is the major defence chemical protecting seedlings and young plant parts against herbivores and other pests. The two isoenzymes hydrolyse DIMBOAGlc with similar kinetics but differ from each other and their sorghum homologues with respect to specificity towards other substrates. To gain insights into the mechanism of substrate (i.e. aglycone) specificity between the two maize isoenzymes and their sorghum homologues, ZMGlu1 was produced in Escherichia coli, purified, crystallized and its structure solved at 2.5 Angstrom resolution by X-ray crystallography. In addition, the complex of ZMGlu1 with the non-hydrolysable inhibitor p-nitrophenyl beta-D-thioglucoside was crystallized and, based on the partial electron density, a model for the inhibitor molecule within the active site is proposed. The inhibitor is located in a slot-like active site where its aromatic aglycone is held by stacking interactions with Trp-378. Whereas some of the atoms on the non-reducing end of the glucose moiety can be modelled on the basis of the electron density, most of the inhibitor atoms are highly disordered. This is attributed to the requirement of the enzyme to accommodate two different species, namely the substrate in its ground state and in its distorted conformation, for catalysis.
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Affiliation(s)
- M Czjzek
- Architecture et Fonction des Macromolecules Biologiques-AFMB-UMR 6098, CNRS and Universités d'Aix-Marseille I et II, 31 Chemin Joseph Aiguier, F13402 Marseille Cedex 20, France.
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