Principles of Biochemistry (2+1)

Folic acid, or folate, consists of the base pteridine attached to one molecule each of p-aminobenzoic acid (PABA) and glutamic acid. Folacin is the generic term for folic acid and related substances having the activity of folic acid.

Functions: Active folate is tetrahydrofolate (H4 folate) (N⁵-formyl-5,6,7,8-tetrahydrofolate). H4 folate is the carrier of activated one-carbon units. The one carbon units carried by H4 folate represent a series in various states in various states of oxidation, namely, methyl, methylene, methenyl, formyl, and forminino. All are metabolically inter convertible.

Deficiency: Folate deficiency causes megaloblastic anemia. N5, N10 –Methylene – H4 folate provides the methyl group in the formation of thymidylate, a necessary precursor of DNA synthesis and erythrocyte formation. Concomitantly with the reduction of the methylene to the methyl group, there is oxidation of H4 folate to dihydrofolate, which must be reconverted to H4 folate for further use. Therefore, cells that synthesize thymidylate (for DNA) are particularly vulnerable to inhibitors of folate reductase such as methotrexate. VitaminB₁₂ and ascorbic acid are both required for the formation of the folic acid coenzymes.

The megaloblastic anemia caused by B₁₂ deficiency may be alleviated by extra folate in the diet, but this treatment will not cure either homocystinuria, methylmalonic aciduria, or the neurologic disorders of B₁₂ deficiency.

RDA

Infants :50µg

Children :100-300µg

Adult (male) :400µg

Adult (female) :400µg

Pregnant women :800µg

Lactating women :600µg

Sources

Richest sources : Yeast, Liver, kidney

Good sources : meat, fish, green leafy vegetables

Fair sources : Milk, fruit.