Further observations on the properties of serum and tissue guanase from man and some animal species. Optimum pH and activation energy in the presence of 8-azaguanine.

The activation energy and the optimum pH of guanine deaminase in man, the rat, guinea pig and mouse were studied using 8-azaguanine as a substrate. The serum guanase in man and in all the animal species studied differs in activation energy from the guanase of the liver. In man, moreover, the serum guanase is also different from the brain and kidney enzyme. In the rat and guinea pig the brain enzyme has thermic activation energy different from the liver and kidney enzyme. The guanase of the serum and tissues of the guinea pig differs from the enzyme of the serum and tissues of man, rat and mouse for optimum pH.