EFFECT OF VARIATIONS IN PROTEIN INTAKE ON ENZYMES OF AMINO ACID METABOLISM

Abstract

Changes in the protein intake of animals result in changes in the activities of many enzymes of nitrogen metabolism. Effects of starvation on enzymes of amino acid metabolism are frequently quite different from effects of ingestion of a protein-free diet. The nature of the changes is such as to suggest that the lability of body proteins depends not on protein intake as such but on the metabolic requirements of the organism. Many of the enzymes of nitrogen metabolism are elevated in starved animals, animals fed a high protein diet, and animals injected with adrenal glucocorticoid hormones. These changes appear to be associated with increasing dependence of the organism on protein metabolism. Many of these enzyme responses to dietary changes can be interpreted as adaptations contributing to the maintenance of homeostasis in the face of alterations in the external environment—alterations that might otherwise affect the internal environment of the organism detrimentally.