Dietary and Hormonal Control of Enzymes of Amino Acid Catabolism in Liver

A high glucose diet fed ad libitum decreased the activities in rat liver of histidase, serine dehydratase, homoserine dehydratase, ornithine transaminase, mitochondrial aspartate transaminase and cytoplasmic alanine transaminase, as compared to normal fed animals. Casein hydrolysate or tryptophan alone given to protein deplted rats increased the hepatic levels of serine dehydratase, alanine transaminase and tyrosine transaminase. Histidase and homoserine dehydratase were increased by casein hydrolysate but not by tryptophan. Aspartate transaminase was increased by tryptophan, but not by casein hydrolysate. Glucose administered intragastrically partly or totally counteracted the induction of serine dehydratase, tyrosine transaminase, cytoplasmic alanine transaminase by cortisol of glucagon administration to protein depleted rats. The similar induction of ornithine transaminase and cytoplasmic aspartate transaminase by cortisol was also counteracted by glucose.