Document Detail


Differences in active site structure in a family of beta-glucan endohydrolases deduced from the kinetics of inactivation by epoxyalkyl beta-oligoglucosides.
MedLine Citation:
PMID:  2494179     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The active sites of a spectrum of beta-glucan endohydrolases with distinct, but related substrate specificities have been probed using a series of epoxyalkyl beta-glycosides of glucose, cellobiose, cellotriose, laminaribiose, laminaritriose, 3O-beta-D-glucosyl-cellobiose and 4O-beta-D-glucosyl-laminaribiose with different aglycon chain lengths. The inactivation of each of the endohydrolases by these compounds results from active site-directed inhibitor action, as indicated by the dependence of the inactivation rate on pH, glycosyl chain length and linkage position, aglycon length, and the protective effect of disaccharides derived from the natural substrates. Comparisons of inhibitor specificity between a Bacillus subtilis 1,3;1,4-beta-D-glucan 4-glucanohydrolase (EC 3.2.1.73), a Streptomyces cellulase (EC 3.2.1.4), a Schizophyllum commune cellulase (EC 3.2.1.4), a Rhizopus arrhizus 1,3-(1,3;1,4)-beta-D-glucan 3(4)-glucanohydrolase (EC 3.2.1.6), and a Nicotiana glutinosa 1,3-beta-D-glucan 3-glucanohydrolase (EC 3.2.1.39) demonstrated different tolerances for glycosyl linkage positions in the inactivation process and a critical role of aglycon length reflecting differences in the active site geometry of the enzymes. For the B. subtilis endohydrolase it was concluded that the aglycon residue of the inhibitor spans the glycosyl binding subsite occupied by the 3-substituted glucosyl residue involved in the glucosidic linkage cleaved in the natural substrate. Appropriate positioning of the inhibitor epoxide group with respect to the catalytic amino acids in the active site is crucial to the inactivation step and the number of glucosyl residues in the inhibitor affects aglycon chain length specificity. The importance of this effect differs between the glucanases tested and may be related to the number of glycosyl binding subsites in the active site.
Authors:
P B Høj; E B Rodriguez; R V Stick; B A Stone
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  264     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1989 Mar 
Date Detail:
Created Date:  1989-04-25     Completed Date:  1989-04-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  4939-47     Citation Subset:  IM    
Affiliation:
Commonwealth Special Research Centre for Protein and Enzyme Technology, Bundoora, Victoria, Australia.
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MeSH Terms
Descriptor/Qualifier:
Bacillus subtilis / enzymology
Binding Sites
Carbohydrate Conformation
Disaccharides
Electrophoresis, Polyacrylamide Gel
Enzyme Activation / drug effects
Epoxy Compounds / pharmacology*
Ethers, Cyclic / pharmacology*
Glycoside Hydrolases / antagonists & inhibitors,  metabolism*
Hydrogen-Ion Concentration
Kinetics
Rhizopus / enzymology
Streptomyces / enzymology
Substrate Specificity
Chemical
Reg. No./Substance:
0/Disaccharides; 0/Epoxy Compounds; 0/Ethers, Cyclic; EC 3.2.1.-/Glycoside Hydrolases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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