Adenylosuccinate synthetase in rat liver: the existence of two types and their regulatory roles.

Rat liver contains two types of adenylosuccinate synthetase which can be distinguished by isoelectroforcusing or immunochemical analysis. One type is identical with the enzyme in rat skeletal muscle (Type M) and the other is specific for the liver (Type L). Type L was more susceptible to nucleotide inhibition, but less susceptible to inhibition by fructose-1,6-diphosphate than Type M. These differences suggest that these isozymes play different regulatory roles in the liver.