title: Escherichia coli pyruvate dehydrogenase complex. Thiamin pyrophosphate-dependent inactivation by 3-bromopyruvate.
abstract: Inactivation of the pyruvate dehydrogenase complex by 3-bromopyruvate is thiamin pyrophosphate (TPP)-dependent. Inactivation with 2-14C- or 3-14C-labeled 3-bromopyruvate results in TPP-dependent covalent labeling of more than 60 sites in the complex, all of which are associated with the dihydrolipoyl transacetylase component. Inactivation by 3-bromo[1-14C]pyruvate labels up to 20 sites associated with dihydrolipoyl transacetylase, also with TPP dependence. Systemic chemical degradation of the complex inactivated by 3-bromo[2-14C]pyruvate under conditions that would convert lipoyl groups to S,S,-biscarboxymethyl dihydrolipoic acid produces S,S,-bis[14C]carboxymethyl dihydrolipoic acid. It is concluded that 3-bromopyruvate inactivates this complex by initially undergoing the first two steps of the usual catalytic pathway, TPP-dependent decarboxylation followed by reductive bromoacetylation of lipoyl moieties. The sulfhydryl groups of S-bromoacetyl dihydrolipoyl moieties generated by reductive bromoacetylation are then alkylated by 3-bromopyruvate as well as by bromoacetyl thioester groups associated with the complex.
mesh_terms: D000345:Affinity Labels / Q000494:pharmacology*; D000478:Alkylation; D002250:Carbon Radioisotopes; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D011773:Pyruvates / Q000494:pharmacology*; D013835:Thiamine Pyrophosphate / Q000037:antagonists & inhibitors*
chemical_list: D000345:Affinity Labels; D002250:Carbon Radioisotopes; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; C017092:bromopyruvate; D013835:Thiamine Pyrophosphate