Open AccessIrreversible Inactivation of Pyruvate Decarboxylase in the Presence of Substrate and an Oxidant
Author(s) -
COGOLIGREUTER Marianne,
HAUSNER Ursula,
CHRISTEN Philipp
Publication year - 1979
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1979.tb02060.x
Subject(s) - chemistry , pyruvate decarboxylase , enzyme , cofactor , substrate (aquarium) , biochemistry , pyruvate dehydrogenase complex , moiety , pyruvate decarboxylation , stereochemistry , biology , ecology , alcohol dehydrogenase
Pyruvate decarboxylase from yeast is progressively inactivated in the presence of pyruvate and an extrinsic oxidant such as 2,6‐dichloroindophenol or hexacyanoferrate(III). The inactivation is linked to the oxidation of the hydroxyethylthiamine diphosphate intermediate to acetate. Removal of low‐molecular compounds by gel filtration does not reactivate the enzyme. The rate of inactivation obeys saturation kinetics with respect to substrate concentration and is independent of enzyme concentration. In analogy to the paracatalytic inactivation of other enzymes forming oxidizable carbanion intermediates [Christen, P. (1977) Methods Enzymol. 46 , 48–54], the oxidation of enzyme‐bound hydroxyethylthiamine diphosphate is thought to generate a transiently reactive intermediate which, without being released from the enzyme, covalently modifies a group at or near the active site. Reconstitution experiments indicate that the protein rather than the coenzyme moiety is modified.