STEADY STATE KINETICS OF RAT BRAIN PYRUVATE DEHYDROGENASE MULTIENZYME COMPLEX

Abstract— The overall steady state kinetic mechanism of pyruvate dehydrogenase multienzyme complex purified from rat brain has been investigated. Initial rate patterns were a series of parallel lines regardless of which substrate was varied at several fixed concentrations of other substrates. Product inhibition patterns showed that acetyl CoA is competitive vs CoA, that NADH is competitive vs NAD, and that both acetyl CoA and NADH are uncompetitive vs pyruvate. Both acetyl CoA and NADH are noncompetitive vs NAD and CoASH, respectively. These results are inconsistent with classical 'hexa uni' ping-pong mechanisms, but are consistent with a non-classical 3-site ping-pong mechanism.