The effects of dietary amino acids on hepatic L-asparagine synthetase.

Rats were fed Roger's synthetic amino acid diets, complete or without asparagine, aspartate, or glutamate, for 2 weeks. Hepatic and serum amino acid content and hepatic asparagine synthetase were assayed before and after the test diets were administered. Special attention was paid to the multiple forms of asparagine synthetase present. Rats fed the test diet without asparagine exhibited high molecular weight (110,000) alpha-form and intermediate molecular weight (57,000) beta-form of asparagine synthetase. Rats fed the complete test diet and the test diet without asparatate exhibited only the beta-form of the enzyme. Rats fed the test diet without glutamate exhibited no enzyme activity. These data are related to the hepatic amino acid levels and to the role of asparagine and asparagine synthetase in amino acid homeostasis.