Folic acid/folate biologically active forms

The vitamin folic acid (folate) is converted to its biologically active form by two successive reductions of the pteridine ring. Both reactions are catalyzed by dihydrofolate reductase. 

Either a primary deficiency of folic acid or functional deficiency secondary to vitamin Bj2 deficiency will have the same effect. In folate deficiency, addition of any biologically active form of folate, but not vitamin B, will normalize the dUMP suppression of [ H]thymidine incorporation. In vitamin B deficiency, addition of vitamin B or methylene-tetrahydrofolate, but not methyl-tetrahydrofolate, will normalize dUMP suppression. 

Folate is the generic name used to refer to a family of vitamers with related biological activity. Instead, folic acid (pteroylglutamin acid, PGA) (Fignre 19.16) refers to the most oxidized, stable, and easily adsorbable synthetic form (monoglutamate). It is commonly nsed in food supplements and in food fortification because of its stability and becomes biologically active after redaction. 

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