All the following biochemical roles of the Ascorbic acid EXCEPT
(Deamination of the hydroxyl group containing amino acids) (134-U.S 3rd) (165-Rana ShindeMetabolic roles and Functions of Ascorbic acid1. Role in cellular Oxidation-Reduction - serving as hydrogen-transport agent2. Role in collagen synthesis - Hydroxy proline and hydroxylysine are important constituents of mature collagen fibres. The are hydroxylated by corresponding "hydroxylases" in presence of vitamin C, Fe++ and molecular O23. Functional activity of Fibroblasts/Osteoblasts - formation of MPS of connective tissue, dentine and intercellular cement substance of capillaries.4. Role in Tryptophan metabolism - as a cofactor for hydroxylation of tryptophan to form 5-OH derivative in the pathway of biosynthesis of serotonin (5-HT)5. Role in Tyrosine metabolism as a cofactor with the enzyme P-OH phenyl pyruvate hydroxylase, which is necessary for hydroxylation and conversion of P-OH phenyl pyruvate to Homogentisic acid (Alkaptonuria)6. Formation of Active FH4 (Tetrahydrofolate) - vitamin-C regulates the conversion of folic acid to folinic acid (so-called citrovorum factor)7. Formation of Ferritin; ATP, NAD+ and NADP+ stimulates the process.8. Absorption of Fe - helps in absorption of Fe in foods. (hypochromic, microcytic anemia)9. Role in electron transport system of mammalian microsomes10. Action on Certain Enzymes-Activation/Inhibition - Arginase and papain are activated, whereas, activity of the enzymes like urease and b-amylase from plants is inhibited11. Role in formation of Catecholamines - as a coenzyme with the enzyme dopamine hydroxylase, which catalyzes the conversion of dopamine to norepinephrine12. Role in formation of Carnitine - Formation of 'carnitine' in liver by hydroxylation by g-butyrobetain13. Role in a-oxidation of fatty acids helps in action of the enzyme a-hydroxylase (a-mono-oxygenase)14. Effect on cholesterol levels - Relation of ascorbic acid with hypocholesterolaemia in man and guinea pigs15. Role in "stress" *The synthesis of bile acids from cholesterol (enzyme-7 a-hydroxylase) is enhanced by ascorbic acid (132-US)16. Vitamin-C has also been reported to act as coenzyme for cathepsins and liver esterases17. Ascorbic acid in both leucocytes and platelets found to be lowered significantly in women taking OCP.18. *Synthesis of corticosteroid hormone - Adrenal gland possess high levels of ascorbic acid, particularly in periods of stress. It is believed that vitamin C is necessary for the hydroxylation reaction in the synthesis of corticosteroid hormone (132-US)19. Sparing action of other vitamins - vitamin C is strong anti-oxidant*. It spares vitamin A, vitamin E, and some B-complex vitamins from oxidation20. Preventive action on cataract - vitamin C reduces the risk of cataract formation* Deamination of the hydroxyl group containing aminoacid requires pyridoxalphosphate
Role of coenzyme in hydroxylation of proline and lysine
Deamination of the hydroxyl group containing amino acids
Steroid biosynthesis
Bile acid synthesis
Vitamins and Minerals