Paracatalytic inactivation of pig heart pyruvate dehydrogenase complex

Balázs Sümegi, István Alkonyi

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The phenomenon of paracatalytic inactivation has been demonstrated and characterized with the pig heart pyruvate dehydrogenase complex. The enzyme became progressively inactive when it was preincubated in the presence of pyruvate, thiamine pyrophosphate, and extrinsic oxidative agent, 2,6-dichloroindophenol. Not only the overall reaction of enzyme complex but the individual reactions catalyzed by enzyme components, pyruvate dehydrogenase, and dihydrolipoamide acetyltrasferase, were reduced after preincubation. The observed inactivation is due to two factors: (i) covalent incorporation of the pyruvate atoms, and (ii) formation of a thiamine pyrophosphate analog. (i) A covalent incorporation of radioactivity from [2-14C]pyruvate into the enzyme complex, which was proportional to the inhibition of overall reaction was observed. Seventy-eight percent of the radioactivity incorporated into the dihydrolipoamide transacetylase but not into the lipoic acid. Thus, modification of the dihydrolipoamide acetyltransferase component can be attributed to the covalent incorporation of pyruvate atoms. (ii) During inactivation, the enzyme-bound thiamine pyrophosphate underwent a modification resulting in the formation of a thiamine pyrophosphate analog, presumably thiamine thiazolone pyrophosphate, which inhibited exclusively the pyruvate dehydrogenase component.

Original languageEnglish
Pages (from-to)417-424
Number of pages8
JournalArchives of Biochemistry and Biophysics
Volume223
Issue number2
DOIs
Publication statusPublished - Jun 1983

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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