The recovery of methionine from homocysteine by transmethylation is depicted in reaction 4. The transmethylation cycle is depicted in reactions 1–4.

Transmethylation is a biologically important organic chemical reaction in which a methyl group is transferred from one compound to another.

An example of transmethylation is the recovery of methionine from homocysteine. In order to sustain sufficient reaction rates during metabolic stress, this reaction requires adequate levels of vitamin B12 and folate. Methyl tetrahydrofolate delivers methyl groups to form the active methyl form of vitamin B12 that is required for methylation of homocysteine. Deficiencies of vitamin B12 or folate cause increased levels of circulating homocysteine. Elevated homocysteine is a risk factor for cardiovascular disease and is linked to the metabolic syndrome (insulin insensitivity).[1]

Transmethylation is decreased sometimes in parents of children with autism.[2]

See also

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References

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  1. ^ Carmel R, Green R, Rosenblatt DS, Watkins D (2003). "Update on cobalamin, folate, and homocysteine" (PDF). Hematology Am Soc Hematol Educ Program. 2003: 62–81. doi:10.1182/asheducation-2003.1.62. PMID 14633777.
  2. ^ James SJ, Melnyk S, Jernigan S, Hubanks A, Rose S, Gaylor DW (November 2008). "Abnormal transmethylation/transsulfuration metabolism and DNA hypomethylation among parents of children with autism". J Autism Dev Disord. 38 (10): 1966–75. doi:10.1007/s10803-008-0591-5. PMC 2584168. PMID 18512136.


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Dimethyltryptamine

hallucinatory symptoms of some psychiatric diseases; this is known as the transmethylation hypothesis. Several speculative and yet untested hypotheses suggest

2-Hydroxybutyric acid

glutathione synthesis become limiting, so homocysteine is diverted from the transmethylation pathway forming methionine into the transsulfuration pathway forming

Folate deficiency

role of vitamin B12 and folate in depression is due to their role in transmethylation reactions, which are crucial for the formation of neurotransmitters

Creatine

intakes of the three precursor amino acids and with the whole body transmethylation flux Creatine synthesis (mmol/day)   8.3 "Creatine". Beth Israel Deaconess

Tryptophan

decarboxylation transforms it into tryptamine [22,25]. Tryptamine then undergoes transmethylation mediated by indolethylamine-N-methyltransferase (INMT) with S-adenosyl

Bufotenin

(April 1999). "Ayahoasca: an experimental psychosis that mirrors the transmethylation hypothesis of schizophrenia". Journal of Ethnopharmacology. 65 (1):

Ergothioneine

dead link] Melville DB, Ludwig ML, Inamine E, Rachele JR (May 1959). "Transmethylation in the biosynthesis of ergothioneine". The Journal of Biological Chemistry

Adenosine kinase

maintenance of methylation reactions. All S-adenosylmethionine-dependent transmethylation reactions in cells lead to production of S-adenosylhomocysteine (SAH)