Metabolism of leucine in protein-calorie-deficient rats.

1. Protein-calorie-depleted rats exhibit a decreased ability to oxidize leucine as compared with control animals. 2. The block in degradation of l-leucine is due to decreased activities of l-leucine transaminase and d-amino acid oxidase associated with liver mitochondria. 3. Cytoplasmic l-leucine transaminase in liver is not affected by the protein depletion. 4. The specific activities of the mitochondrial enzymes can be increased by a single oral dose of 1g. of Bacto-Peptone (meat hydrolysate). The effect of Bacto-Peptone can be inhibited by prior administration of dosages of 10mg. of puromycin/100g. body wt., suggesting that the increased enzyme specific activities may be due to new synthesis of enzyme protein.