In the pyruvate dehydrogenase complex (and also the -ketoglutarate dehydrogenase complex), the carboxyl group of lipoic acid is joined to dihydrolipoamide transacetylase via an amide bond linking the carboxyl group of lipoic acid to a lysine -amino group of the enzyme. The resulting reactive species is an amide, called lipoamide.

-Keto Acid Complexes - A Review