Studies on Escherichia coli Pyruvate Dehydrogenase Complex

Abstract

Bromopyruvate inactivates the pyruvate dehydrogenase complex of Escherichia coli in a thiamine pyrophosphate (TPP)-dependent process. The catalytic activities of the individual enzyme components within the complex are not destroyed by bromopyruvate under similar conditions, but the activities of the pyruvate dehydrogenase and dihydrolipoyl dehydrogenase components are reduced in thiamine pyrophosphate-independent processes. Radioactivity from [2-14C]bromopyruvate is irreversibly bound in the presence or absence of thiamine pyrophosphate, but the amount of radioactivity bound in the presence of thiamine pyrophosphate is 3.9 times the amount bound in its absence. The data are consistent with the interpretation that TPP-dependent inactivation involves the action of bromopyruvate as an irreversible inhibitor which is directed into the complex by specific, but not necessarily irreversible, interaction with the pyruvate dehydrogenase component and ultimately blocks some site within the complex which is essential for catalytic activity in the over-all reaction but not in partial reactions catalyzed by the component enzymes.