coworkers as an acetate replacing factor 1'2 and is insoluble
in water, but soluble in organic solvents. It is
known by a variety of names, including thioctic acid; 1,
2-dithiolane-3pentanoic acid; 1, 2-dithiolane-3 valeric
acid; and 6,8-thioctic acid. As lipoamide, it functions
as a cofactor in the multienzyme complexes that catalyze
the oxidative decarboxylation of a-keto acids such
as pyrnvate, ct-ketoglutarate, and branched chain aketo
acids) c~-Lipoic acid was tentatively classified as
a vitamin after its isolation, 1'4 but it was later found to
be synthesized by animals and humansS; however, the
complete enzyme pathway that is responsible for the
de novo synthesis has not yet been elucidated. Several
studies indicate that octanoate serves as the immediate
precursor for the 8-carbon fatty acid chain, and cysteine
appears to be the source of sulfur. 6