Yeast Pyruvate Kinase

Abstract

The kinetic properties of purified yeast pyruvate kinase were investigated. The enzyme showed cooperative kinetics toward the essential activating monovalent cations K+ and NH4+, Mg2+, and phosphoenolpyruvate. Fructose 1,6-diphosphate, which yielded homotropic cooperative kinetics and did not affect maximal velocity, transformed the sigmoidal kinetics of K+ and NH4+, Mg2+, and phosphoenolpyruvate to hyperbolic and lowered the apparent Km for each variable. Adenosine diphosphate, however, exhibited no cooperativity and was relatively unaffected by fructose 1,6-diphosphate. The enzyme displayed a complex velocity dependence on pH.