C-1-tetrahydrofolate synthase, cytoplasmic also known as C1-THF synthase is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the MTHFD1 (methylenetetrahydrofolate dehydrogenase 1) gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

This gene encodes a protein that possesses three distinct enzymatic activities, methylenetetrahydrofolate dehydrogenase

Methylenetetrahydrofolate dehydrogenase (NADP+)

In enzymology, a methylenetetrahydrofolate dehydrogenase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 5,10-methylenetetrahydrofolate and NADP+, whereas its 3 products are 5,10-methenyltetrahydrofolate, NADPH, and H+.This enzyme belongs to the family...

 (1.5.1.5), methenyltetrahydrofolate cyclohydrolase

Methenyltetrahydrofolate cyclohydrolase

In enzymology, a methenyltetrahydrofolate cyclohydrolase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 5,10-methenyltetrahydrofolate and H2O, whereas its product is 10-formyltetrahydrofolate....

 (3.5.4.9) and formate–tetrahydrofolate ligase (6.3.4.3). Each of these activities catalyzes one of three sequential reactions in the interconversion of 1-carbon derivatives of tetrahydrofolate

Tetrahydrofolic acid

Tetrahydrofolic acid, or tetrahydrofolate, is a folic acid derivative.-Metabolism:-Human synthesis:It is produced from dihydrofolic acid by dihydrofolate reductase...

, which are substrates for methionine

Methionine

Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...

, thymidylate

Thymidine monophosphate

Thymidine monophosphate, also known as 5'-thymidylate, thymidylate, or TMP, is a nucleotide that is used as a monomer in DNA. It is an ester of phosphoric acid with the nucleoside thymidine. TMP consists of a phosphate group, the pentose sugar deoxyribose, and the nucleobase thymine...

, and de novo purine

Purine

A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....

syntheses. The trifunctional enzymatic activities are conferred by two major domains, an aminoterminal portion containing the dehydrogenase and cyclohydrolase activities and a larger synthetase domain.