5-Methyltetrahydrofolate-homocysteine methyltransferase

5-methyltetrahydrofolate-homocysteine methyltransferase
Identifiers
Symbol	MTR
Entrez	4548
HUGO	7468
OMIM	156570
RefSeq	NM_000254
UniProt	Q99707
Other data
EC number	2.1.1.13
Locus	Chr. 1 q43

5-Methyltetrahydrofolate-homocysteine methyltransferase or (MTR) is an enzyme responsible for the production of methionine from homocysteine. MTR forms part of the S-adenosyl methionine cycle and is also called methionine synthase.

Function

MTR contains the cofactor - methylcobalamin (MeB₁₂) and uses the substrates N5-methyl-tetrahydrofolate (N⁵-methyl-THF) and homocysteine.

The enzyme works in two steps in a ping-pong reaction. First, methylcobalamin is formed by a methyl group transfer from N⁵-mTHF with formation of MeB₁₂ and tetrahydrofolate (THF). In the second step, MeB₁₂ transfers this methyl group to (homocysteine), regenerating the cofactor cobalamin and releasing the product methionine

File:VitaminB12 2.png

The MTR reaction

See also

• methyltransferase
• Arakawa's syndrome II
• 5-methyltetrahydrofolate

External links

• ENZYME: EC 2.1.1.13
• 5-Methyltetrahydrofolate-Homocysteine+S-Methyltransferase at the US National Library of Medicine Medical Subject Headings (MeSH)