Hepatic induction of threonine dehydratase and tryptophan pyrrolase to tyrotoxic rats.

The levels of hepatic threonine dehydratase and tryptophan pyrrolase are elevated in 5% tyrosine-fed rats, and these increases are dependent on the dietary tyrosine level. Experiments with RNA and protein synthesis inhibitors indicate that the appearance of these new enzyme activities are dependent on concomitant new protein synthesis and the inducer operates at a transcriptional level.