Abstract
When added directly to the assay medium under standard conditions, 3-bromopyruvate inhibited wheat dihydrodipicolinate synthase (DHDPS) competitively with respect to pyruvate and uncompetitively with respect to aspartate semialdehyde. When DHDPS was incubated with 3-bromopyruvate at pH 7.5 and 30°C, this reagent irreversibly inactivated the enzyme. The inactivation followed pseudofirst-order kinetics during the early period of inactivation; then the inactivation rate decreased. For the early period of inactivation, the pseudo-first-order rate constant was 0.29 min-1 and the Ki of 3-bromopyruvate was 1.8mM. Pyruvate protected against inactivation, while aspartate semialdehyde partially did so and lysine did not. The Hill constant for lysine of the enzyme inactivated by 73 % was about half of that of the untreated enzyme.
