OPTION 2

 

•            Folic acid or folacin (Latin :folium-leaf) is abundantly found in green leafy vegetables.

•            lt is important for one carbon metabolism and is required for the synthesis of certain amino acids, purines and the pyrimidine-thymine.

•            The active form of folic acid is tetrahydrofolate (THF or FH).

•            lt is synthesized from folic acid by the enzyme dihydrofolatereductase.

•            The reducing equivalents are provided by 2 moles of NADPH.

•            Tetrahydrofolate(THF or FH) ,the coenzyme of folic acid, is actively involved in the one carbon metabolism.

•            THF serves as an acceptor or donor of one carbon units (formyl, methyl etc.) in a variety of reactions involving amino acid and nucleotide metabolism.

Role of folic acid in one carbon metabolism

DHF: Dihydrofolate; FIGLU: Formiminoglutamate; THF; Tetrahydrofolate;

dUMP: Deoxyuridine monophosphate; TMP: Thymidine monophosphate; PLP: Pyridoxal phosphate

 

Deficiency Manifestations

Folate deficiency frequently occurs particularly in pregnant women and in alcoholics.

Clinical symptoms of folic acid deficiency include:

•            Megaloblastic or macrocytic anemia: The deficiency of folic acid leads to impairment of synthesis of DNA. Impaired DNA synthesis, impairs the maturation of erythrocytes. Consequently, megaloblasts are formed instead of normoblast. These megaloblasts are accumulated in the bone marrow and leads to megaloblastic anemia.

•            Accumulation and excretion of FIGLU in the urine: Folate deficiency blocks the last step of histidine catabolism, due to lack of THF. This results in accumulation of FIGLU in body, which leads to increased excretion of FIGLU in urine.

•            Hyperhomocysteinemia: Due to folic acid deficiency the methylation of homocysteine to methionine is impaired which leads to hyperhomocysteinemia. Increased level of homocysteine is a risk factor for cardiovascular disease.

•            Neural tube defect in fetus: Since, folate is required for the formation of neural tube in early stage of gestation, the folate deficiency during early stage of pregnancy increases the risk of neural tube defect.