Cofactors

Abstract

Whereas plants and certain microorganisms can generate all required coenzymes from CO 2 or simple organic precursors, animals must obtain precursors (designated as vitamins) for a major fraction of their coenzymes from nutritional sources. Still, most vitamins must be converted into the actual coenzymes by reactions catalyzed by animal enzymes. The structures and biosynthetic pathways of some coenzymes are characterized by extraordinary complexity. Enzymes for coenzyme biosynthesis have frequently low catalytic rates, and some of them catalyze reactions with highly unusual mechanisms.Many coenzymes (cofactors) involved in human and animal metabolism were discovered in the first half of the twentieth century, and their isolation and structure elucidation were hailed as milestones as shown by the impressive number of Nobel prizes awarded for research in that area. Studies on coenzyme biosynthesis were typically initiated in the second half of the twentieth century and have generated a massive body of literature that continues to grow rapidly because the area still involves many incompletely resolved problems. In parallel, numerous novel coenzymes were discovered relatively recently by studies of microorganisms. In this chapter, the terms "cofactor" and "coenzyme" are used as synonyms.Cofactor biosynthesis is a very broad and multifaceted topic. This chapter summarizes basic concepts of major cofactors. Detailed status reports on the