Induction of multiple forms of tyrosine aminotransferase by amino acid mixtures of different compositions

Hepatic tyrosine aminotransferase (EC 2.6.1.5) was induced in rats by intubation of amino acid mixtures (complete or tryptophan-free). Enzyme activity was increased 4-fold by the complete mixture and 8-fold by the tryptophan-free mixture. The enzyme was analyzed by chromatography on CM-Sephadex. Chromatographic patterns were characteristic of the type of inducer rather than of the chronology of the induction cycle: after induction by the complete amino acid mixture the three forms of the enzyme were equally increased whereas after induction by the tryptophan-free mixture Form I was preferentially increased.