These coenzymes are biotin and lipoate. Biotin is a coenzyme for carboxylase enzymes; it is a water-soluble B-vitamin, also called vitamin [tex] B_{7} [/tex]. Lipoate or lipoic acid is made normally in animals. Actually, lipoate is a conjugate base of lipoic acid. It is covalently attached by an amide bond to a lysine.