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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
2001-1-2
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pubmed:abstractText |
Steady-state kinetic studies of the enzymic glucosyl transfer to and from phosphate catalysed by cellobiose phosphorylase from Cellulomonas uda have shown that this enzyme operates by a ternary-complex kinetic mechanism in which beta-cellobiose binds before phosphate, and beta-D-glucose and alpha-D-glucopyranosyl phosphate are released in that order. alpha-D-Glucopyranosyl fluoride (but not beta-D-glucopyranosyl fluoride) serves as alternative glucosyl donor for beta-cellobiose synthesis with a specificity constant that is one-ninth that of the corresponding enzymic reaction with alpha-D-glucopyranosyl phosphate (approximately 20000 M(-1).s(-1) at 30 degrees C). The kinetic parameters for a complete series of deoxy and deoxyfluoro analogues of D-glucose have been determined and the data yield estimates of the net strengths of hydrogen-bonding interactions with the non-reacting hydroxy groups of D-glucose at the transition state (0.8-4.0 kcal/mol, where 1 cal identical with 4.184 J) and enable the prediction of the polarities of these hydrogen bonds. Each hydroxy group functions as donor of a hydrogen for bonding to probably a charged (at 3-OH) or neutral (at 2-OH and 6-OH) acceptor group on the enzyme. The equatorial 1-OH is essential for enzyme activity. Derivatives of D-glucose in which the 1-OH or the reacting 4-OH were replaced by hydrogen or fluorine have been tested as inhibitors to measure their affinities for the sugar-binding subsite +1 (numbered from the bond-cleaving/forming site). The data show that hydrogen-bonding interactions between the 1-OH and 4-OH and charged groups on the enzyme stabilize the ground-state ternary complex of the enzymic synthesis of beta-cellobiose by 2.3 and 0.4 kcal/mol, respectively, and assist the precise positioning of beta-D-glucose for catalysis.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/11042119-10218105,
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Nov
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pubmed:issn |
0264-6021
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
1
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pubmed:volume |
351 Pt 3
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
649-59
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
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pubmed:year |
2000
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pubmed:articleTitle |
Role of non-covalent enzyme-substrate interactions in the reaction catalysed by cellobiose phosphorylase from Cellulomonas uda.
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pubmed:affiliation |
Institute of Food Technology, University of Agricultural Sciences (BOKU), Muthgasse 18, A-1190 Vienna, Austria. nide@edv2.boku.ac.at
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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