Lipoate is an essential cofactor for five redox reactions; four in oxoacid dehydrogenases (active in energy metabolism and amino acid metabolism) and one in the glycine cleavage system (GCS). Lipoate synthesis in mitochondria requires three steps. In the first step, mitochondrial lipoyltransferase 2 (LIPT2) transfers an octanoyl group bound to an acyl-carrier protein (most likely NDUFAB1, acyl-carrier protein, ACP) to mitochondrial glycine cleavage system H protein (GCSH) at lysine 107. The human protein is thought to function in the same way as yeast LIP2 (Schonauer et al. 2009).