A comparison of the effect of diet and of ethionine on rat liver histidine deaminase and urocanase

Abstract

Low levels of ethionine, when fed or injected, cause a marked decrease in the level of rat liver urocanase activity but produce a slight increase in the level of histidine deaminase (histidine ammonia-lyase, EC 4.3.1.3) activity. Fasting or feeding a protein-free diet results in decreased activities of both enzymes. These findings support the suggestion that ethionine does not inhibit urocanase through general inhibition of protein synthesis.Methionine, whether fed or injected, reduces the magnitude of the effect of ethionine on urocanase, but subcutaneously injected ATP and related compounds do not.