Mechanism of renaturation of pyruvate kinase of Saccharomyces carlsbergensis: activation by L-valine and magnesium and manganese ions.

Pyruvate kinase (EC 2.7.1.40) of S. carlsbergensis is a tetrameric enzyme, composed of four identical subunits each of which contains 1 mole of L-valine noncovalently bound. The enzyme readily dissociates into monomeric units. L-Valine and magnesium or manganese ions are specific primers of the renaturation process of the enzyme. The amino acid induces renaturation with a K(0.5) of 17 muM and a pseudo first-order rate constant of 0.019 min(-1) at 25 degrees with respect to the monomeric species, indicating that L-valine influences the folding of the monomeric form from a disordered state to its native conformation being followed by a spontaneous reassociation with formation of the tetrameric enzyme. Independently, magnesium and manganese ions induce the renaturation with a first-order rate constant of the same magnitude.