A potential energy profile of the catalytic cycle of pyruvate decarboxylase

Abstract

A computational study on the mechanism for the decarboxylation of pyruvic acid to acetaldehyde catalyzed by pyruvate decarboxylase at the B3LYP/6-31G (<i>d</i>, <i>p</i>) level of theory is presented. The model employed is self-contained and it does not resort to external groups to provide protons to the various structures in the mechanism. The potential energy surface points at the intramolecular proton transfer from the amino group of the pyrimidine ring in the enamine intermediate to the enol exocyclic carbon as the rate-determining step (with a barrier of 20.55 kcal·mol<sup>–1</sup>). This value is in reasonable agreement with an estimated barrier of 24.76 kcal·mol<sup>–1</sup>, derived from the experimental rate constant (4.0 10<sup>–5</sup> s<sup>–1</sup>) for the decarboxylation of α-lactylthiamin