The activation of l-threonine dehydrogenase by potassium ions

Abstract

Staphylococcus aureus threonine dehydrogenase is partially inactivated by dialysis against water, but the dialysed enzyme can be activated by incubation with KC1 at 0[degree]. Maximal activation requires incubation in 0.5 [image],-KCl for 24 hr. The activation is unaffected by the presence of EDTA. The enzyme is activated by Rb+, Cs+, K+, NH4+ and to a smaller extent by Li+ and Na+ ions. As well as the time dependent activation, the enzymic activity is stimulated by the addition of KC1 to the assay mixture. The specificities of the 2 activating effects are similar. The active form of the enzyme is probably a K+ ion-apoenzyme complex. The K+ ions in the assay mixture may act by maintaining the equilibrium in favor of complex-formation.