Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a

folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...

derivative.

Metabolism

Human synthesis

Tetrahydrofolic acid is produced from

dihydrofolic acid Dihydrofolic acid (conjugate base dihydrofolate) (DHF) is a folic acid ( vitamin B9) derivative which is converted to tetrahydrofolic acid by dihydrofolate reductase. Since tetrahydrofolate is needed to make both purines and pyrimidines, which ar ...

by dihydrofolate reductase. This reaction is inhibited by methotrexate. It is converted into

5,10-methylenetetrahydrofolate 5,10-Methylenetetrahydrofolate (N5,N10-Methylenetetrahydrofolate; 5,10-CH2-THF) is cofactor in several biochemical reactions. It exists in nature as the diastereoisomer R5,10-methylene-THF. As an intermediate in one-carbon metabolism, 5,10-CH2 ...

serine hydroxymethyltransferase Serine hydroxymethyltransferase (SHMT) is a pyridoxal phosphate (PLP) (Vitamin B6) dependent enzyme () which plays an important role in cellular one-carbon pathways by catalyzing the reversible, simultaneous conversions of L-serine to glycine ...

Bacterial synthesis

Many bacteria use

dihydropteroate synthetase Dihydropteroate synthase is an enzyme classified under . It produces dihydropteroate in bacteria, but it is not expressed in most eukaryotes including humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PA ...

to produce

dihydropteroate Dihydropteroate is an important intermediate in folate synthesis. It is a pterin created from ''para''-aminobenzoic acid (PABA) by the enzyme dihydropteroate synthase. Bacteriostatic agents such as sulfonamides target dihydropteroate synthetas ...

, a molecule without function in humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PABA precursor.

Functions

Tetrahydrofolic acid is a cofactor in many reactions, especially in the synthesis (or anabolism) of

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

s and nucleic acids. In addition, it serves as a carrier molecule for single-carbon moieties, that is, groups containing one carbon atom e.g. methyl, methylene, methenyl, formyl, or formimino. When combined with one such single-carbon moiety as in 10-formyltetrahydrofolate, it acts as a donor of a group with one carbon atom. Tetrahydrofolate gets this extra carbon atom by sequestering

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

produced in other processes. These single-carbon moieties are important in the formation of precursors for DNA synthesis. A shortage in tetrahydrofolic acid (FH4) can cause

megaloblastic anemia Megaloblastic anemia is a type of macrocytic anemia. An anemia is a red blood cell defect that can lead to an undersupply of oxygen. Megaloblastic anemia results from inhibition of DNA synthesis during red blood cell production. When DNA synth ...

. Methotrexate acts on dihydrofolate reductase, like

pyrimethamine Pyrimethamine, sold under the brand name Daraprim among others, is a medication used with leucovorin (leucovorin is used to decrease side effects of pyrimethamine; it does not have intrinsic anti-parasitic activity) to treat the parasitic dise ...

trimethoprim Trimethoprim (TMP) is an antibiotic used mainly in the treatment of bladder infections. Other uses include for middle ear infections and travelers' diarrhea. With sulfamethoxazole or dapsone it may be used for ''Pneumocystis'' pneumonia in peo ...

, as an inhibitor and thus reduces the amount of tetrahydrofolate made. This may result in megaloblastic anemia. Tetrahydrofolic acid is involved in the conversion of formiminoglutamic acid to glutamic acid; this may reduce the amount of

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the d ...

available for decarboxylation and protein synthesis, and hence the urinary histamine and formiminoglutamic acid may be decreased. Image:Dihydrofolic acid.svg,

Dihydrofolic acid Dihydrofolic acid (conjugate base dihydrofolate) (DHF) is a folic acid ( vitamin B9) derivative which is converted to tetrahydrofolic acid by dihydrofolate reductase. Since tetrahydrofolate is needed to make both purines and pyrimidines, which ar ...

Image:5,10-methylenetetrahydrofolic acid.svg, 5,10-Methylenetetrahydrofolic acid Image:10-formyl-tetrahydrofolic acid.svg, 10-Formyltetrahydrofolic acid

References

External links

Tetrahydrofolate bound to proteins
in the PDB {{DEFAULTSORT:Tetrahydrofolic Acid Folates Coenzymes