The activity of the BCKDH complex, rate-limiting enzyme for branched-chain amino acid catabolism, is regulated by a phosphorylation / dephosphorylation cycle. BCKDH kinase is responsible for inactivation of the complex. This study investigated the mechanism responsible for a sex difference in regulation of liver BCKDH activity state. Sprague-Dawley rats were fed high-protein. (30% or 50%) semi-synthetic diets or commercial chow diet for 3 weeks. Regardless of dietary protein, female rats had much lower liver BCKDH activity states than male rats. The activity state of the BCKDH complex in female rats also did not change markedly with dietary protein. However, the activity of BCKDH kinase was higher (1.5-3 fold) in female than in male rats. Ovariectomy of females caused a marked increase in liver BCKDH activity state (from 7% active to 80% active), but castration of males produced no change. These results suggest: (a) the amount of BCKDH kinase is an important determinant of BCKDH activity state and (b) female hormones suppress the activity state of BCKDH and prevent the male-type response to high-protein diets. Supported by DK19259.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology