ROLE OF COENZYMES AS VITAMIN IN METABOLISM

Vitamins that serve as precursors of coenzymes are principally the B vitamins. These substances occur not only in the free form but also in bound forms from which they must be liberated in the digestive tract by appropriate secreted enzymes before they can be utilized. The transport of vitamins from the digestive tract into the bloodstream and to various cells and finally into the cells may require specific transport proteins for a particular vitamin. Within the cells, most members of the group of B vitamins are converted into coenzyme forms which are required for the activity of specific enzymes. Such a coenzyme may be attached by ionic, coordinate covalent, or, in some cases, covalent bonding to an apoenzyme to provide an enzyme (holoenzyme) catalyzing a specific reaction.