AN UNUSUAL STABLE ADDUCT IN THE REACTION OF PYRUVATE WITH PAPAIN CHEMICALLY-MODIFIED BY 3-ACETYL PYRIDINIUM AND QUINOLINIUM DERIVATIVES

We have previously shown that electrophilic carbonyl compounds includi ng ethyl pyruvate are slowly reduced by 3-acetyl-1,4-dihydropyridines attached to the active site thiol group of papain(1). The mechanism of this reaction has been investigated using sodium 2-[C-13]-pyruvate as substrate. In contrast, reduction did not occur but the formation of an unexpected stable adduct assigned to the enol of the heterocyclic p rosthetic groups to C-2 of pyruvate was observed.