<prompt> Man can not synthesise ascorbic acid due to deficiency of enzymeL gulanolactone oxidaseGluco cerbrosidasePeroxidaseLysyl oxidase  <response>: ASCORBIC ACID VITAMIN C:The active form of vitamin C is ascorbic acid. Its main function is as a reducing agent. Vitamin C is a coenzyme in hydroxylation reactions for example, hydroxylation of prolyl and lysyl residues in collagen where its role is to keep the iron Fe of hydroxylases in the reduced, ferrous Fe2 form. Thus, vitamin C is required for the maintenance of normal connective tissue as well as for wound healing. Vitamin C also facilitates the absorption of dietary nonheme iron from the intestine by reduction of the ferric form Fe3 to Fe2.Man and other primates, guinea pigs and bats cannot synthesize ascorbic acid due to the deficiency of a single enzyme namely L-gulonolactone oxidase.Key Concept:Man cannot synthesize ascorbic acid due to the deficiency of a single enzyme namely L-gulonolactone oxidase.Ref : Lippincotts illustrated reviews for biochemistry , 7th edition. 