A revised preparation of yeast (Saccharomyces cerevisiae) pyruvate kinase.

A revised preparation of pyruvate kinase from saccharomyces cerevisiae is reported. By purifying this cold-labile enzyme at room temperature, an improved recovery and specific activity was obtained. More than 350 mg of pure enzyme with a specific activity of 350 to 400 units/mg at 30 degrees were obtained from a pound of fresh yeast. The last step of the preparation, passage of the enzyme over Sephadex G-100, was required to remove a contaminating protease. The molecular parameters of the new preparation are: molecular weight, 209,000; four subunits of identical size; E 280 nm, 0.51; pI 6.6; and pH optimum, 6.28. Kinetic parameters are: Km for P-enolpyruvate and ADP, 0.09 and 0.18 mM in the presence of saturating Fru-1,6-P2, and 1.8 and 0.34 mM in the absence of Fru-1,6-P2; Ka for Fru-1,6-P2, 0.014 mM. No free NH2-terminal amino acid could be detected. Amino acid composition was determined and compared with other pyruvate kinase preparations.