Progress in establishing the rate-limiting features and kinetic mechanism of the glyceraldehyde-3-phosphate dehydrogenase reaction.
Primary hydrogen isotope effects and steady-state kinetics have been used to study the mechanism of glyceraldehyde-3-phosphate (GAP) dehydrogenase at pH 8.6. The isotope effect determined by using GAP-1d was unity and independent of arsenate (used as the acyl acceptor) and NAD+ concentrations when the aldehyde substrate was at saturating concentrations. At low GAP concentrations (apparent V/K conditions), the primary hydrogen isotope effect (H/D) was in the range of 1.40-1.52 and independent of arsenate and NAD+ concentrations. Apparent V/K for NAD+ was independent of GAP concentration, and apparent V/K for GAP was independent of NAD+ concentration. The dependence of apparent V/K for GAP on arsenate concentration was more complex but extrapolated to nonzero V/K at the zero-arsenate intercept. These observations are consistent with the general features of the Segal and Boyer (1953) mechanism for the reaction.
Liu
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Department of Chemistry, Rutgers, State University of New Jersey, Newark 07102.
Huskey
W P
WP
D001149:Arsenates / Q000378:metabolism; D005986:Glyceraldehyde 3-Phosphate / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009243:NAD / Q000378:metabolism
D001149:Arsenates; D009243:NAD; D005986:Glyceraldehyde 3-Phosphate; D006859:Hydrogen; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C025657:arsenic acid