Studies of the effect of ionic compounds on the stability of glutamate dehydrogenase

Abstract

Abstract 1. 1. Glutamate dehydrogenase ( l -glutamate: NAD(P) oxidoreductase (deaminating), EC 1.4.1.3), in solution in the absence of protective ions, is rapidly inactivated as the pH of the solution is raised to 8 or higher. The addition of some ionic compounds greatly retards this alkaline inactivation. 2. 2. Alkaline phosphate and ammonium salts are among the best protective agents; Tris is one of the least effective. 3. 3. The inactivation of glutamate dehydrogenase in aqueous solutions appears to pass through stages which include conversion of an active form, relatively resistant to inhibition by progesterone, dicumarol, o- phenanthroline , thyroxine and fluorenyl-acetamide, to another active form which is more susceptible to the action of these inhibitors. 4. 4. The rapidity of these changes in the glutamate dehydrogenase molecule is related to the nature of the salt solution used to suspend the crystalline enzyme and to that used to dissolve and dilute this suspension.