Mechanisms of biosynthesis of protein-derived redox cofactors

Prior to 1990, redox cofactors were widely believed to be small molecule, dissociable compounds. In the past 10 years, however, four novel redox cofactors have been discovered, each of which is derived from posttranslational modification of specific amino acids within their cognate enzymes. These include topa quinone, found in copper amine oxidases, lysine tyrosyl quinone, found in lysyl oxidase, tryptophan tryptophylquinone, found in methylamine dehydrogenase, and the cysteine-cross-linked tyrosine found in galactose oxidase. The processes by which these cofactors are formed, called biogenesis, is currently a major focus of mechanistic work in this field. In this review, the latest progress toward elucidating the various biogenesis mechanisms is discussed, along with possible linkages between the chemistries involved in catalysis and biogenesis.