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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
44
|
| pubmed:dateCreated |
1995-12-18
|
| pubmed:abstractText |
Transient kinetic data for D-xylose reduction with NADPH and NADPD and for xylitol oxidation with NADP+ catalyzed by recombinant C298A mutant human aldose reductase at pH 8 have been used to obtain estimates for each of the rate constants in the complete reaction mechanism as outlined for the wild-type enzyme in the preceding paper (Grimshaw et al., 1995a). Analysis of the resulting kinetic model shows that the nearly 9-fold increase in Vxylose/Et for C298A mutant enzyme relative to wild-type human aldose reductase is due entirely to an 8.7-fold increase in the rate constant for the conformational change that converts the tight (Ki NADP+ = 0.14 microM) binary *E.NADP+ complex to the weak (Kd NADP+ = 6.8 microM) E.NADP+ complex from which NADP+ is released. Evaluation of the rate expressions derived from the kinetic model for the various steady-state kinetic parameters reveals that the 37-fold increase in Kxylose seen for C298A relative to wild-type aldose reductase is largely due to this same increase in the net rate of NADP+ release; the rate constant for xylose binding accounts for only a factor of 5.5. A similar 17-fold increase in the rate constant for the conformational change preceding NADPH release does not, however, result in any increase in Vxylitol/Et, because hydride transfer is largely rate-limiting for reaction in this direction.(ABSTRACT TRUNCATED AT 250 WORDS)
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Nov
|
| pubmed:issn |
0006-2960
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
7
|
| pubmed:volume |
34
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
14366-73
|
| pubmed:dateRevised |
2007-11-14
|
| pubmed:meshHeading | |
| pubmed:year |
1995
|
| pubmed:articleTitle |
Human aldose reductase: subtle effects revealed by rapid kinetic studies of the C298A mutant enzyme.
|
| pubmed:affiliation |
Whittier Diabetes Program, Department of Medicine, University of California, San Diego, La Jolla 92093-0983, USA.
|
| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
|