Studies on the Decarboxylation of Pyruvate.II.Kinetic Studies on the Binding of Thiamine Pyrophosphate to Pyruvate Decarboxylase

Abstract

The reconstitution of pyruvate decarboxylase has been studied kinetically in thepresence of several concentrations of thiamine pyrophosphate (TPP) and Mn²⁺. The Km for TPP determined graphically was decreased by increasing Mn²⁺ concentration, while V_max was almost unchanged. The values of Kms for Mn²⁺ and V_max, were affected in mixed manner by the amount of TPP.
The significance of Kms thus determined is discussed and the values are compared to that determined in transketolase.