5,10-Methylenetetrahydrofolate (5,10-CH₂-THF) is the substrate

Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

 used by the 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...

 methylenetetrahydrofolate reductase

Methylenetetrahydrofolate reductase

Methylenetetrahydrofolate reductase is an enzyme that in humans is encoded by the MTHFR gene. Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine...

 (MTHFR) to generate 5-methyltetrahydrofolate

5-Methyltetrahydrofolate

Levomefolic acid or metafolin is the natural, active form of folic acid used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine among other functions. The un-methylated form, folic acid , is a synthetic form of folate found in nutritional supplements...

 (5-MTHF).
5,10-CH₂-THF can also be used as a coenzyme in the biosynthesis

Biosynthesis

Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 of thymidine

Thymidine

Thymidine is a chemical compound, more precisely a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine in double-stranded DNA...

. More specifically it is the C1-donor in the reactions catalyzed by thymidylate synthase

Thymidylate synthase

Thymidylate synthetase is the enzyme used to generate thymidine monophosphate , which is subsequently phosphorylated to thymidine triphosphate for use in DNA synthesis and repair....

 and thymidylate synthase (FAD)

Thymidylate synthase (FAD)

In enzymology, a thymidylate synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are 5,10-methylenetetrahydrofolate, dUMP, and FADH2, whereas its 3 products are dTMP, tetrahydrofolate, and FAD....

. It also acts as a coenzyme in the synthesis of serine from glycine via the enzyme serine hydroxymethyl transferase.