Biosynthesis of lipoic acid in the rat: incorporation of 35S- and 14C-labeled precursors.
ABSTRACT After injection of various 35S- and 14C-containing compounds, the incorporation of the label into the lipoic acid present in the liver of growing rats has been determined. The best precursor for sulfur atoms, after 24 h, is cysteine; methionine and cystamine are scarcely incorporated and thiosulfate not at all. Good precursors of the carbon moiety are acetate and octanoate, whereas the incorporation of butyrate and cysteine is very low. It is concluded that lipoic acid is biosynthesized in the rat liver, and that sulfur atoms probably originate from cysteine.