Effect of Thyroxine on Liver Tyrosine-glutamic Acid Transaminase

Abstract

Aging the soluble rat liver tyrosine oxidase system which converts tyrosine to fuma-rate and acetoacetate decreased the activity of oxidative enzymes thus leaving tyrosine-glutamic acid transaminase and tautomerase in a coupled system. Thyroxine, in concentrations as low as 5 x 10-5 [image] markedly inhibited this system. The transaminase enzyme appeared to be most directly involved, as judged by difference studies using recording spectrophotometric techniques.