Methenyltetrahydrofolate Cyclohydrolase
An aminohydrolase that catalyzes the hydrolysis of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate. In most higher eucaryotic organisms this enzyme also includes METHYLENETETRAHYDROFOLATE DEHYDROGENASE (NADP) and FORMATE-TETRAHYDROFOLATE LIGASE activities.
Formate-Tetrahydrofolate Ligase
Methylenetetrahydrofolate Dehydrogenase (NADP)
An NADP-dependent oxidoreductase that catalyses the conversion of 5,10-methyleneterahydrofolate to 5,10-methenyl-tetrahydrofolate. In higher eukaryotes a trifunctional enzyme exists with additional METHENYLTETRAHYDROFOLATE CYCLOHYDROLASE and FORMATE-TETRAHYDROFOLATE LIGASE activity. The enzyme plays an important role in the synthesis of 5-methyltetrahydrofolate, the methyl donor for the VITAMIN B12-dependent remethylation of HOMOCYSTEINE to METHIONINE via METHIONINE SYNTHETASE.
Aminohydrolases
GTP Cyclohydrolase
(GTP cyclohydrolase I) or GTP 7,8-8,9-dihydrolase (pyrophosphate-forming) (GTP cyclohydrolase II). An enzyme group that hydrolyzes the imidazole ring of GTP, releasing carbon-8 as formate. Two C-N bonds are hydrolyzed and the pentase unit is isomerized. This is the first step in the synthesis of folic acid from GTP. EC 3.5.4.16 (GTP cyclohydrolase I) and EC 3.5.4.25 (GTP cyclohydrolase II).
Carbon-Nitrogen Ligases
Formyltetrahydrofolates
Tetrahydrofolates which are substituted by a formyl group at either the nitrogen atom in the 5 position or the nitrogen atom in the 10 position. N(5)-Formyltetrahydrofolate is leukovorin (citrovorum factor) while N(10)-formyltetrahydrofolate is an active coenzyme which functions as a carrier of the formyl group in a number of enzymatic reactions.
Deoxyribodipyrimidine Photo-Lyase
Phosphoribosylaminoimidazolecarboxamide Formyltransferase
Ligases
Glycine Hydroxymethyltransferase
Leucovorin
The active metabolite of FOLIC ACID. Leucovorin is used principally as an antidote to FOLIC ACID ANTAGONISTS.
Folic Acid
A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (POACEAE). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.
Carbon-Carbon Lyases
Rhodocyclaceae
A family of gram-negative bacteria in the order Rhodocyclales, class BETAPROTEOBACTERIA. It includes many genera previously assigned to the family PSEUDOMONADACEAE.