FIGURE 1.

The human pathway of assembly of lipoyl moieties on its cognate proteins. LIPT2 utilizes octanoyl-ACP synthesized by the mitochondrial fatty acid synthesis system to modify GCSH. The reaction proceeds via a LIPT2 acyl enzyme intermediate as shown. The octanoyl-GCSH is then converted to lipoyl-GCSH by LIAS catalyzed sulfur insertion. LIPT1 then transfers the lipoyl moiety from GCSH to form an acyl enzyme intermediate. This in turn is attacked by a specific lysine reside of the lipoyl domain (LD) of the N-termini of the E2 subunits of the dehydrogenases or GCSH to give the active modified enzymes.