The activity of branched-chain alpha-keto acid dehydrogenase complex in rat digestive tracts: Effects of dietary protein and exercise.

Branched-chain alpha-keto acid dehydrogenase complex is the rate limiting enzyme in catabolism of branched-chain amino acids. In this study, we examined effects of dietary protein and exercise on the complex activity in digestive tracts (stomach, small intestine and colon) of rats. Rats were fed a high (30%) or low (8%) protein diet for 3 weeks and a half of rats in each diet group was exercised by 85 min running just prior to sacrifice on the final day of the experiment. Total and actual (active form) activities of the complex were markedly high in stomach compared to other two tissues and the actual activity in stomach was significantly elevated by exercise only in rats fed the high protein diet. Both total and actual activities in colon were only a few percentage of those in stomach, and those in small intestine was further less. These results suggest that rat stomach is the tissue active in catabolism of branched-chain amino acids, which is promoted by combination of high protein diet and exercise.