Trimethylglycine
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Trimethylglycine (also commonly known as TMG, betaine, glycine betaine or betaine anhydrous) is more specifically N,N,N-trimethylglycine.
TMG is not to be confused with betaine hydrochloride.
Trimethylglycine is an organic compound with a structure similar to choline and a betaine. The molecular structure is (CH3)3NCH2COOH as a cation with either the carboxylic acid as the anion (loss of proton) or another anion present. The difference is that choline (trimethylaminoethanol) has been reduced from a terminal carboxylic acid to a hydroxyl group. If Trimethylglycine donates one of its methyl groups, then it becomes dimethylglycine.
Alkylated derivates of Trimethylglycine have use as quaternary ammonium zwitterionic surfactants.
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[edit] Therapeutic uses
Trimethylglycine is used to treat high homocysteine levels.[1] Kilmer S McCully MD theorised that cholesterol and clogged arteries were symptoms rather than causes of heart disease and proposed homocysteine as a more likely culprit. If it were not for his work, homocysteine would not have been thought harmful and so supplements to lower homocysteine would not have been thought necessary.
TMG may also have uses in enhancing mood.
A compound which may be confused with TMG is betaine hydrochloride, or betaine HCl. Betaine HCl is used as a digestive aid; it is particularly helpful for persons with insufficient acid production in the stomach. Betaine HCl has an acidic taste. TMG (anhydrous betaine) does not.
[edit] Biochemical mechanisms
TMG functions very closely with choline, folic acid, vitamin B12 and S-adenosyl methionine SAMe. All of these compounds function as "methyl donors." They carry and donate methyl functional groups to facilitate necessary chemical processes. The donation of methyl groups is important to proper liver function, cellular replication, and detoxification reactions. TMG also plays a role in the manufacture of carnitine and serves to protect the kidneys from damage.
Methyl donors, DNA and cancer - DNA methylation is central to the establishment and heritability of states of expression. Gene silencing that is dependent on DNA methylation involves histone deacetylation. The relevance of the correct maintenance of these modification patterns is illustrated by cancer, in which alterations in DNA methylation occur. Hypomethylation is associated with chromosomal instability. [2] Methionine is formed from Homocysteine and is converted to SAMe, the human body's predominant methyl donor. In 1985, studies were conducted into Methionine metabolism and cancer. One paper summarised the most recent developments linking methionine metabolism and SAMe to DNA methylation and gene expression in relation to cancer. The study stated that "recent evidence suggests that enzymatic DNA methylation is an important component of gene control and may serve as a silencing mechanism for gene function. Some carcinogens interfere with enzymatic DNA methylation, and thus may allow oncogene activation". The author (J van der Westhuyzen) also wrote that demethylation may be a necessary condition for enhanced transcription and pointed out that DNA hypomethylation has been observed in many cancer cells and tumours. [3] In 2002 LL Wu and JT Wu of the University of Utah Health Science Centre published a study [4] making the claim that circulating total Homocysteine "may be used as a more accurate tumour marker for monitoring cancer patients during treatment, and hyperhomocysteinemia [may be used] as a risk factor for carcinogenesis". Trimethylglycine / betaine donates a methyl group to convert homocysteine to methionine (using Vitamin B6 and Zinc as co-factors) in a reaction catalysed by BHMT (the Betaine-Homocysteine-Methyl-Transferase enzyme). Methionine is then converted to SAMe by Methionine Adenosyl Transferase (MAT) using Magnesium and Adenosine Triphosphate as co-factors.
[edit] Trimethylglycine in Molecular Biology
Trimethylglycine is an adjuvant of the Polymerase Chain Reaction (PCR) and of all DNA polymerisation based assays such as DNA sequencing. By an unknown Function it aids in the prevention of secondary structures in the DNA molecules and prevents the problems associated with the amplification and sequencing of GC rich regions. Trimethylglycine makes Guanosine and Cytidine (Strong binders) behave with thermodynamics similar to those of Thymidine and Adenosine (Weak Binders). It is best used at a final concentration of 1M.
[edit] References
- ^ Holm PI, Ueland PM, Vollset SE, Midttun O, Blom HJ, Keijzer MB, den Heijer M. (2005) Betaine and folate status as cooperative determinants of plasma homocysteine in humans. Arterioscler Thromb Vasc Biol. 379-85. PMID 15550695
- ^ doi: 10.1038/npg.els.006158
- ^ Nutr Cancer 1985; 7(3):179-83
- ^ Clin Chim Acta 2002 Aug;322(1-2):21-8
[edit] External links
- USDA Database for the Choline Content of Common Foods - including the data on choline metabolites, such as betaine, in 434 food items.
- Links to external chemical sources.
