Role of vitamins on protein metabolism
1. Thiamine (vitamin B₁). Thiamine helps the enzyme system which is
responsible for the synthesis of fats from proteins.
2. Pyridoxine (vitamin B₁). This vitamin takes part in the normal
tryptophan metabolism, being a constituent of the enzyme kynureninase,
responsible for conversion of kynurenine to anthranilic acid and 3-hydroxy
kynurenine to 3-hydroxyanthranilic acid. Pyridoxine acts as a prosthetic group
for the enzyme transaminase and as a coenzyme for those enzymes which
decarboxylate tyrosine, arginine, glutamic acid and 3, 4-dihydroxy
phenylalanine (DOPA).
3. Cyanocobalamin (vitamin B₁2). This plays an important
role in the synthesis of nucleic acid. Deficiency of it causes a disturbance of
the DNA metabolism. This vitamin helps in connection with the formation of
methyl groups and in the reactions of transmethylation as in the bio synthesis
of methionine. It acts as coenzyme and has been found to catalyze the enzymatic
conversion of glutamate to 8-methyl aspartate in bacterial system and to catalyze
the isomerase reaction in animal tissues where methyl malonyl CoA is converted
to succinyl CoA.
4. Biotin (vitamin H). Biotin is linked up with riboflavin. It acts as
a coenzyme and helps in decarboxylation. It also helps in the deamination of
threonine, serine and aspartic acid.
5. Ascorbic acid (vitamin C). This vitamin helps in the development of
protein matrix in the bones. Ascorbic acid takes part in the oxidation of
-hydroxyphenyl pyruvic acid to homogentisic acid which is the intermediate
metabolic end product of tyrosine metabolism.
6. Folic acid. It is related with nucleoprotein metabolism. The
reduced form of folic acid known as tetrahydrofolic acid acts as a coenzyme in
the transfer of formyl and hydroxymethyl group in the biosynthesis of purines.
7. Riboflavin. Riboflavin is a constituent of FMN and FAD which act as
coenzymes in enzyme system, e.g., L-amino acid oxidase, xanthine oxidase, and
thus related to protein metabolism.
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