Title: THE EFFECT OF UNIVALENT CATION SALTS ON PROPERTIES OF PYRUVATE KINASE Abstract approved: Redacted for Privacy

Experiments described to determine the effect of a series of univalent cation salts on the physical properties of crystalline pyru-vate kinase, an enzyme that has an absolute requirement for unival-ent cations for activity, are reported. An investigation of the stabil-ity of the enzyme in a series of different salt solutions revealed marked effects of different univalent cation species and of different species of anions. A strong positive correlation was shown between the capacity of univalent cations to protect against inactivation of the enzyme and to activate pyruvate kinase. In addition, potassium, an activator cation, restored to a considerable extent enzyme activity that was lost due to incubation of the enzyme in solutions of the non-activator cations, lithium and Tris. The enzyme consistently showed more stability in buffer solutions containing multivalent anions such as pyrophosphate, sulfate, phosphate and arsenate than in buffer solutions containing the univalent anions acetate, bromide, nitrat