Properties of yeast pyruvate decarboxylase and their modification by proteolytic enzymes: I. Stability of decarboxylases from wild-type and mutant strains

Abstract

High concentrations of inorganic phosphate and ammonium sulfate stabilize yeast pyruvate decarboxylase to heating at 60 ° for long periods of time in the presence of TPP and Mg +. When heated at 60 ° in phosphate concentrations above 1.6 m, addition of cofactors is not necessary to stabilize native enzyme. TPP alone, in the absence of divalent cations, is sufficient to stabilize enzyme resolved for cofactors when the enzyme is heated at 60 ° in 1.0 m phosphate. High concentrations of TPP are capable of activating resolved enzyme for ability to decarboxylate pyruvate without added divalent cations. Pyruvate decarboxylase present in extracts of a mutant yeast strain was found to be unstable in acetaldehyde-forming capacity but relatively stable in ability to synthesize acetylmethylcarbinol (AMC).