Effect of Diets and Hormones on Two Urea Cycle Enzymes.

All treatments increasing protein catabolism produced an increase in arginine synthetase activity. Arginase activity was increased only in cases where the increased protein breakdown was accompanied by an increase or maintenance of body weight. The changes in lactic acid dehydrogenase, used as a control enzyme, more nearly parallel those in arginase and show very little relationship to changes in arginine synthetase. It has been suggested that arginine synthetase would be a better indicator enzyme of nitrogen catabolism than arginase.