Metabolism of folic acid

B,2 Cobalamin Coenzyme in transfer of one-carbon fragments and metabolism of folic acid Pernicious anemia = megaloblastic anemia with degeneration of the spinal cord... 

MTX interferes with the growth of cancer cells by inhibiting the metabolism of folic acid. Drug efficacy was evaluated in vitro by MTT assay, as described above, and by Trypan Blue exclusion. Trypan Blue is a non-vital dye excluded by viable cells, but selectively staining dead cells. According to Figure 13.7, higher suppression of cell... 

One form of remethylation deficit involves defective metabolism of folic acid, a key cofactor in the conversion of homocysteine to methionine 677... 

Recently, tritiated folic acid became available, making possible a nonmicrobiological method for studying the metabolism of folic acid. It obviates the toxic effects of folic acid antagonists on microbial assay organisms. This technique was used to follow the uptake, metabolism, and excretory products of folic acid (A4, J2, J3). 

H20. Hutner, S. H., Nathan, H. A., and Baker, H., Metabolism of folic acid and other pterin-pteridine vitamins. Vitamins and Hormones 17, 1-52 (1959). 

Fused pyrimidines inhibiting enzymes active in metabolism of folic acid as new antitumor substances 91KFZ(9)20. 

The metabolism of folic acid involves reduction of the pterin ting to different forms of tetrahydrofolylglutamate. The reduction is catalyzed by dihydtofolate reductase and NADPH functions as a hydrogen donor. The metabolic roles of the folate coenzymes are to serve as acceptors or donors of one-carbon units in a variety of reactions. These one-carbon units exist in different oxidation states and include methanol, formaldehyde, and formate. The resulting tetrahydrofolylglutamate is an enzyme cofactor in amino acid metabolism and in the biosynthesis of purine and pyrimidines (10,96). The one-carbon unit is attached at either the N-5 or N-10 position. The activated one-carbon unit of 5,10-methylene-H folate (5) is a substrate of T-synthase, an important enzyme of growing cells. 5-10-Methylene-H folate (5) is reduced to 5-methyl-H,j folate (4) and is used in methionine biosynthesis. Alternatively, it can be oxidized to 10-formyl-H folate (7) for use in the purine biosynthetic pathway. 

C20H23N7O7, Mr 473.45, pale yellow crystals +3 H2O, mp. 248 -250 °C (decomp.), [a]n +16.8° (aqueous hydrogen carbonate). F. occurs in various microorganisms in which it acts as a growth factor e. g., for the lactic acid bacterium Leuconostoc citrovorum, therefore, it is also known as citrovorum factor. F. functions as an active 1-C unit (cf. folic acid) and formyl group transfer agent in the metabolism of folic acid tetrahy-drofolic acid. F. is accessible by synthesis and its calcium salt is used therapeutically as an antidote for folic acid antagonists such as methotrexate. 

Metabolism of Folic Acid and Other Pterin-Pteridine Vitamins... 

Vitamin deficiency causes pernicious anaemia — the release into the bloodstream of immature precursors of red blood cells (megaloblastic anaemia). As discussed in section 11.11.3.2, vitamin B deficiency impairs the metabolism of folic acid, leading to the development of functional folate deficiency this is what disturbs the rapid multiplication of red blood cells, causing immature precursors to be released into the circulation. 

Orotic acid is utilized by the body in the metabolism of folic acid and vitamin B-12. Also, it appears to aid the replacement or restoration of some cells. There is indication that vitamin B-13 may be helpful in the treatment of multiple sclerosis. 

FUNCTIONS. The specific biochemical functions of vitamin C are not clearly understood. Nevertheless, it is established as a very important substance for body welfare because of being implicated in the following roles (1) formation and maintenance of collagen, which makes for more rapid and sound healing of wounds and burns (2) metabolism of the amino acids tyrosine and tryptophan (3) absorption and movement of iron (4) metabolism of fats and lipids, and cholesterol control (5) as an antioxidant in the protection of vitamins A and E and the polyunsaturated fatty acids (6) sound teeth and bones (7) strong capillary walls and healthy blood vessels (8) metabolism of folic acid and perhaps in a number of other roles. Details follow ... 

Metabolism of folic acid (folacin)—Vitamin C is required for the conversion of the inactive form of the vitamin, folic acid (folacin), to its active form, folinic acid. When there is an insufficiency of vitamin C in the diet, the metabolism of folic acid (folacin) is impaired and the megaloblastic anemia that occurs in scurvy, and sometimes in infancy, may result... 

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