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Fumarate Activation and Kinetic Solvent Isotope Effects as Probes of the NAD-Malic Enzyme Reaction

The kinetic mechanism of activation of the NAD-malic enzyme by fumarate and the transition state structure for the oxidation malate for the NAD-malic enzyme reaction have been studied. Fumarate exerts its activating effect by decreasing the off-rate for malate from the E:Mg:malate and E:Mg:NAD:malate complexes. The activation by fumarate results in a decrease in K_imalate and an increase in V/K_malate by about 2-fold, while the maximum velocity remains constant. A discrimination exists between active and activator sites for the binding of dicarboxylic acids. Activation by fumarate is proposed to have physiologic importance in the parasite. The hydride transfer transition state for the NAD-malic enzyme reaction is concerted with respect to solvent isotope sensitive and hydride transfer steps. Two protons are involved in the solvent isotope sensitive step, one with a normal fractionation factor, another with an inverse fractionation factor. A structure for the transition state for hydride transfer in the NAD-malic enzyme reaction is proposed.

Identiferoai:union.ndltd.org:unt.edu/info:ark/67531/metadc278864
Date12 1900
CreatorsLai, Chung-Jeng
ContributorsCook, Paul F., Harris, Ben G., Dobson, Gerard R., Yorio, Thomas, Wu, Edward Ming-chi, 1938-, Gracy, Robert W., Harris, Elizabeth H.
PublisherUniversity of North Texas
Source SetsUniversity of North Texas
LanguageEnglish
Detected LanguageEnglish
TypeThesis or Dissertation
Formatix, 98 leaves : ill., Text
RightsPublic, Copyright, Copyright is held by the author, unless otherwise noted. All rights reserved., Lai, Chung-Jeng

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