5-Methyltetrahydrofolate-homocysteine methyltransferase

5-Methyltetrahydrofolate-homocysteine methyltransferase

5-methyltetrahydrofolate-homocysteine methyltransferase, also known as MTR, is a human gene.cite web | title = Entrez Gene: MTR 5-methyltetrahydrofolate-homocysteine methyltransferase| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=4548| accessdate = ]

PBB_Summary
section_title =
summary_text = "MTR" encodes the enzyme 5-methyltetrahydrofolate-homocysteine methyltransferase. This enzyme, also known as cobalamin-dependent methionine synthase, catalyzes the final step in methionine biosynthesis. Mutations in MTR have been identified as the underlying cause of methylcobalamin deficiency complementation group G.cite web | title = Entrez Gene: MTR 5-methyltetrahydrofolate-homocysteine methyltransferase| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=4548| accessdate = ]

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. [cite journal |author=Banerjee RV, Matthews RG |title=Cobalamin-dependent methionine synthase |journal=FASEB J. |volume=4 |issue=5 |pages=1450–9 |year=1990 |pmid=2407589 |url=http://www.fasebj.org/cgi/reprint/4/5/1450.pdf]

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


MTR is the only mammalian enzyme that metabolizes 5-methylTHF to regenerate the active cofactor, tetrahydrofolate. Deficiency in MTR function may be due to genetic mutations, reduced levels of its cobalamin cofactor (vitamin B12), or decreased levels of the enzyme methionine synthase reductase (required for the sustained activity of MTR).

The consequence of reduced MTR activity is megaloblastic anemia.

Genetics

Several polymorphisms in "MTR" have been identified.2756A->G (Asp919Gly)

ee also

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

References

Further reading

PBB_Further_reading
citations =
*cite journal | author=Banerjee RV, Matthews RG |title=Cobalamin-dependent methionine synthase. |journal=FASEB J. |volume=4 |issue= 5 |pages= 1450–9 |year= 1990 |pmid= 2407589 |doi=
*cite journal | author=Ludwig ML, Matthews RG |title=Structure-based perspectives on B12-dependent enzymes. |journal=Annu. Rev. Biochem. |volume=66 |issue= |pages= 269–313 |year= 1997 |pmid= 9242908 |doi= 10.1146/annurev.biochem.66.1.269
*cite journal | author=Matthews RG, Sheppard C, Goulding C |title=Methylenetetrahydrofolate reductase and methionine synthase: biochemistry and molecular biology. |journal=Eur. J. Pediatr. |volume=157 Suppl 2 |issue= |pages= S54–9 |year= 1998 |pmid= 9587027 |doi=
*cite journal | author=Garovic-Kocic V, Rosenblatt DS |title=Methionine auxotrophy in inborn errors of cobalamin metabolism. |journal=Clinical and investigative medicine. Médecine clinique et experimentale |volume=15 |issue= 4 |pages= 395–400 |year= 1992 |pmid= 1516297 |doi=
*cite journal | author=O'Connor DL, Moriarty P, Picciano MF |title=The impact of iron deficiency on the flux of folates within the mammary gland. |journal=International journal for vitamin and nutrition research. Internationale Zeitschrift für Vitamin- und Ernährungsforschung. Journal international de vitaminologie et de nutrition |volume=62 |issue= 2 |pages= 173–80 |year= 1992 |pmid= 1517041 |doi=
*cite journal | author=Everman BW, Koblin DD |title=Aging, chronic administration of ethanol, and acute exposure to nitrous oxide: effects on vitamin B12 and folate status in rats. |journal=Mech. Ageing Dev. |volume=62 |issue= 3 |pages= 229–43 |year= 1992 |pmid= 1583909 |doi=
*cite journal | author=Vassiliadis A, Rosenblatt DS, Cooper BA, Bergeron JJ |title=Lysosomal cobalamin accumulation in fibroblasts from a patient with an inborn error of cobalamin metabolism (cblF complementation group): visualization by electron microscope radioautography. |journal=Exp. Cell Res. |volume=195 |issue= 2 |pages= 295–302 |year= 1991 |pmid= 2070814 |doi=
*cite journal | author=Li YN, Gulati S, Baker PJ, "et al." |title=Cloning, mapping and RNA analysis of the human methionine synthase gene. |journal=Hum. Mol. Genet. |volume=5 |issue= 12 |pages= 1851–8 |year= 1997 |pmid= 8968735 |doi=
*cite journal | author=Gulati S, Baker P, Li YN, "et al." |title=Defects in human methionine synthase in cblG patients. |journal=Hum. Mol. Genet. |volume=5 |issue= 12 |pages= 1859–65 |year= 1997 |pmid= 8968736 |doi=
*cite journal | author=Leclerc D, Campeau E, Goyette P, "et al." |title=Human methionine synthase: cDNA cloning and identification of mutations in patients of the cblG complementation group of folate/cobalamin disorders. |journal=Hum. Mol. Genet. |volume=5 |issue= 12 |pages= 1867–74 |year= 1997 |pmid= 8968737 |doi=
*cite journal | author=Chen LH, Liu ML, Hwang HY, "et al." |title=Human methionine synthase. cDNA cloning, gene localization, and expression. |journal=J. Biol. Chem. |volume=272 |issue= 6 |pages= 3628–34 |year= 1997 |pmid= 9013615 |doi=
*cite journal | author=Wilson A, Leclerc D, Saberi F, "et al." |title=Functionally null mutations in patients with the cblG-variant form of methionine synthase deficiency. |journal=Am. J. Hum. Genet. |volume=63 |issue= 2 |pages= 409–14 |year= 1998 |pmid= 9683607 |doi=
*cite journal | author=Salomon O, Rosenberg N, Zivelin A, "et al." |title=Methionine synthase A2756G and methylenetetrahydrofolate reductase A1298C polymorphisms are not risk factors for idiopathic venous thromboembolism. |journal=Hematol. J. |volume=2 |issue= 1 |pages= 38–41 |year= 2002 |pmid= 11920232 |doi= 10.1038/sj/thj/6200078
*cite journal | author=Watkins D, Ru M, Hwang HY, "et al." |title=Hyperhomocysteinemia due to methionine synthase deficiency, cblG: structure of the MTR gene, genotype diversity, and recognition of a common mutation, P1173L. |journal=Am. J. Hum. Genet. |volume=71 |issue= 1 |pages= 143–53 |year= 2002 |pmid= 12068375 |doi=
*cite journal | author=De Marco P, Calevo MG, Moroni A, "et al." |title=Study of MTHFR and MS polymorphisms as risk factors for NTD in the Italian population. |journal=J. Hum. Genet. |volume=47 |issue= 6 |pages= 319–24 |year= 2002 |pmid= 12111380 |doi= 10.1007/s100380200043
*cite journal | author=Doolin MT, Barbaux S, McDonnell M, "et al." |title=Maternal genetic effects, exerted by genes involved in homocysteine remethylation, influence the risk of spina bifida. |journal=Am. J. Hum. Genet. |volume=71 |issue= 5 |pages= 1222–6 |year= 2003 |pmid= 12375236 |doi=
*cite journal | author=Zhu H, Wicker NJ, Shaw GM, "et al." |title=Homocysteine remethylation enzyme polymorphisms and increased risks for neural tube defects. |journal=Mol. Genet. Metab. |volume=78 |issue= 3 |pages= 216–21 |year= 2004 |pmid= 12649067 |doi=

External links

* [http://www.expasy.org/cgi-bin/enzyme-search-ec ENZYME: EC 2.1.1.13]
*

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