Tyrosine aminotransferase in frog liver

1. In frog liver, tyrosine aminotransferase is located mainly in cytoplasm. The enzyme is an anionic protein of mol. wt. 115 000 daltons, specific toward 2-oxoglutarate. The enzyme separates on ion-exchange chromatography into two active forms. 2. Administration of triiodotyronine in vivo induces the activity of the enzyme. Epinephrine and glucagon have no effect, and cAMP and insulin repress this activity by about 70%. 3. Triiodotyronine stimulates incorporation of [14C]leucine into protein, and the amount of the enzyme in the nacent polysome-bound protein is considerably increased.