Acetylphosphinate is the most potent mechanism-based substrate-like inhibitor of both the human and Escherichia coli pyruvate dehydrogenase components of the pyruvate dehydrogenase complex

TitleAcetylphosphinate is the most potent mechanism-based substrate-like inhibitor of both the human and Escherichia coli pyruvate dehydrogenase components of the pyruvate dehydrogenase complex
Publication TypeJournal Article
Year of Publication2006
AuthorsNemeria, NS, Korotchkina LG, Chakraborty S, Patel MS, Jordan F
JournalBioorganic Chemistry
Volume34
Pagination362-379
Date PublishedDec
Type of ArticleArticle
ISBN Number0045-2068
Accession Numberhttp://apps.isiknowledge.com/InboundService.do?Func=Frame&product=WOS&action=retrieve&SrcApp=EndNote&Init=Yes&SrcAuth=ResearchSoft&mode=FullRecord&UT=000242677800005
Keywordsacetoin, acetylmethylphosphinate, acetylphosphinate, acetylphosphonate methyl ester, BINDING, circular dichroism, COENZYME, DEHYDROGENASE COMPLEX, E1 SUBUNIT, ENZYMES, Escherichia coli pyruvate, human pyruvate dehydrogenase complex, INACTIVATION, inhibition, INTERMEDIATE, mechanism-based, MULTIENZYME COMPLEX, SLOW-BINDING, TAUTOMERIC FORM, thiamin 2-thiothiazolone diphosphate, THIAMIN DIPHOSPHATE
Abstract

Two analogues of pyruvate, acetylphosphinate and acetylmethylphosphinate were tested as inhibitors of the E1 (pyruvate dehydrogenase) component of the human and Escherichia coli pyruvate dehydrogenase complexes. This is the first instance of such studies on the human enzyme. The acetylphosphinate is a stronger inhibitor of both enzymes (K-i < 1 mu M) than acetylmethylphosphinate. Both inhibitors are found to be reversible tight-binding inhibitors. With both inhibitors and with both enzymes, the inhibition apparently takes place by formation of a C2 alpha-phosphinolactylthiamin diphosphate derivative, a covalent adduct of the inhibitor and the coenzyme, mimicking the behavior of substrate and forming a stable analogue of the C2 alpha-lactylthiamin diphosphate. Formation of the intermediate analogue in each case is confirmed by the appearance of a positive circular dichroism band in the 305-306 nm range, attributed to the 1',4'-iminopyrimidine tautomeric form of the coenzyme. It is further shown that the alpha His63 residue of the human E1 has a role in the formation of C2 alpha-lactylthiamin diphosphate since the alpha His63Ala variant is only modestly inhibited by either inhibitor, nor did either compound generate the circular dichroism bands assigned to different tautomeric forms of the 4'-aminopyrimidine ring of the coenzyme seen with the wild-type enzyme. Interestingly, opposite enantiomers of the carboligase side product acetoin are produced by the human and bacterial enzymes. (c) 2006 Elsevier Inc. All rights reserved.

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Alternate JournalBioorganic Chem.