Abstract
Microbial protease inhibitors, bestatin and leupeptin, were per fused through hindquarters, and the effects of these inhibitors on the amino acid release and the accumulation of acid soluble peptides were studied using normal and Streptozotocin-induced diabetic rats. Both inhibitors depressed the amino acid release from the hindquarters of normal rats. However, leupeptin, unlikebestatin, failed to suppress the release of amino acids in diabetic rats. Bestatin caused an accumulation of acid soluble peptides in per fused skeletal muscle. However, leupeptin did not show this effect. The amino acid composition and the N-terminal amino acids were analyzed on the acid soluble peptides accumulated after bestatin per fusion. Branched-chain amino acids were preferentially accumulated as the acid soluble peptides, and more than half of the total amounts of these amino acids were located in the N-terminus. From these results, it was concluded that bestatin-sensitive protease(s), probably leucine aminopeptidase and/or arylamidase, play an important role in the degradation process of skeletal muscle proteins, especially in the steps to degrade acid soluble peptides into free amino acids.
