Cobalamin-dependent formation of leucine and beta-leucine by rat and human tissue. Changes in pernicious anemia.

Circulating levels of beta-leucine are elevated in the cobalamin-deficient state of pernicious anemia. Levels of leucine, on the other hand, are much lower. It is proposed that leucine 2,3-aminomutase, the cobalamin-dependent enzyme that catalyzes the interconversion of leucine and beta-leucine, is the affected enzyme in pernicious anemia and causes these results by preventing the synthesis of leucine from beta-leucine. The synthesis of leucine by human leukocytes and hair roots and by rat liver extracts has been shown to occur when either branched chain fatty acids or valine metabolites are the substances. The synthesis is dependent upon adenosylcobalamin and is inhibited by intrinsic factor.