Kinetic mechanism of pyruvate decarboxylase Evidence for a specific protonation of the enzymic intermediate

Abstract
Decarboxylation of pyruvate by pyruvate decarboxylase (EC 4.1.1.1) was performed in a reaction mixture containing 50% deuterium. The isolated product, acetaldehyde, was investigated directly by 1H NMR and by mass spectrometry after conversion to the 2,4‐dinitrophenyl hydrazone. The protium content of 56% at acetaldehyde Cl demonstrate a specific protonation of the corresponding intermediate by the enzyme. Proton inventory studies and enzyme modification indicate the 4′ amino group of the coenzyme, thiamine pyrophosphate, in an immonium structure being a possible proton donor. A ‘partially concerted’ mechanism is suggested for the reaction steps following the decarboxylation.

This publication has 10 references indexed in Scilit: