The rate of oxidation of L-[1-14C] leucine to 14CO2 by isolated rat hepatocytes is increased by pyruvate and dichloroacetate. This effect is specific for L-leucine not being observed for L-valine, L-isoleucine, or D-leucine. Transamination, the rate-limiting step of L-leucine catabolism in the liver, is the site of stimulation, because uptake of L-leucine by the cells and the oxidation of its transamination product, α-ketoisocaproate, are not increased. Measurement of steady state levels of α-ketoisocaproate indicate that both pyruvate and dichloroacetate promote the transamination of L-leucine, thereby increasing the availability of substrate for decarboxylation by the α-ketoisocaproate dehydrogenase complex (EC 18.104.22.168). Pyruvate stimulation of transamination is secondary to the provision of keto acid acceptors for the amino group of L-leucine. The mechanism of the effect of dichloroacetate remains unknown.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - Jan 1 1978|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology