| Autor: |
Urbauer JL; Institute for Enzyme Research, Department of Biochemistry, University of Wisconsin, Madison 53705, USA., Bradshaw DE, Cleland WW |
| Jazyk: |
angličtina |
| Zdroj: |
Biochemistry [Biochemistry] 1998 Dec 22; Vol. 37 (51), pp. 18018-25. |
| DOI: |
10.1021/bi981819g |
| Abstrakt: |
3-Fluorooxalacetate is a substrate for malic dehydrogenase. When enzymatic reduction is slower than the rate of epimerization of the two enantiomers, only (2R,3R)-erythro-fluoromalate is formed. Conversely, when a high enzyme level and excess of NADH lead to reduction that is fast relative to the epimerization rate, equal amounts of (2R,3R)-erythro- and (2R,3S)-threo-fluoromalate are formed. These data suggest that the V/K value for reduction of the R enantiomer to give the erythro isomer is approximately 100 times greater than for reduction of the S enantiomer to give the threo isomer. The equilibrium constant for the oxidation of fluoromalate is an order of magnitude less favorable than for oxidation of malate, while the equilibrium deuterium isotope effect from deuteration at C-2 of the substrate is 1.09 for fluoromalate versus 1.18 for malate. These effects reflect the inductive effect of fluorine at the 3-position. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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