Cofactor-Dependent Enzymes and Cofactor Regeneration
A number of enzymatic reactions require cofactors, some of the common inorganic cofactors being iron/sulphur clusters and metalloporphyrins. These cofactors are costly and therefore can not be used in industry, unless regenerated as a reaction by-product. Some of the cofactors which can be recycled effectively include the following: (i) nucleoside triphosphates, such as ATP in phosphoryl-transfer reactions, (ii) nicotinamide adenine dinucleotide (NAD) and its 3' phosphate (NADP) in oxidoreductions, (iii) acetyl CoA in acyl transfer reactions, (iv) 3' -phosphoadenosine- 5' - phosphosulphate (PAPS) in the formation l of sulphate esters and (v) sugar nucleotides in glycosyl transfer reactions. Many cofactor dependent reactions involving regeneration of cofactor have been used for industry. However regeneration of cofactor may require additional enzymes, whose number may be reduced by using bifunctional enzymes.