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|Related amino acids||Glycine
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Trimethylglycine (TMG) is an organic compound that occurs in plants. Trimethylglycine was the first betaine discovered by science; originally it was simply called betaine because, in the 19th century, it was discovered in sugar beets. Since then, many other betaines have been discovered, and the more specific name glycine betaine distinguishes this one.
Structure and reactions
Trimethylglycine is an N-trimethylated amino acid. This quaternary ammonium exists as the zwitterion at neutral pH. Strong acids such as hydrochloric acid converts TMG to various salts, HCl yielding betaine hydrochloride:
- (CH3)3N+CH2CO2- + HCl → [(CH3)3N+CH2CO2H]Cl-
Production and biochemical processes
Processing sucrose from sugar beets yields glycine betaine as a byproduct. The value of the TMG rivals that of the sugar content in sugar beets. Glycine betaine production involves chromatographic separation.
In most organisms, glycine betaine is biosynthesized by oxidation of choline in two steps. The intermediate, betaine aldehyde, is generated by the action of the enzyme mitochondrial choline oxidase (choline dehydrogenase, EC 184.108.40.206). Betaine aldehyde is further oxidised in the mitochondria or cytoplasm to betaine by the enzyme called betaine aldehyde dehydrogenase (EC 220.127.116.11).
TMG is an organic osmolyte that occurs in high concentrations (10s of millimolar) in many marine invertebrates, such as crustaceans and molluscs. It serves as a potent appetitive attractant to generalist carnivores such as the predatory sea-slug Pleurobranchaea californica.
TMG is an important cofactor in methylation, a process that occurs in every cell of mammals to synthesize and donate methyl groups (CH3) for other processes in the body. These processes include the synthesis of neurotransmitters such as dopamine, serotonin. Methylation is also required for the biosynthesis of melatonin and the electron transport chain constituent coenzyme Q10.
The major step in the methylation cycle is the remethylation of homocysteine, which can occur via either of two pathways. The major pathway involves the enzyme methionine synthase, which requires vitamin B12 as a cofactor, and also depends indirectly on folate and various other B vitamins. The minor pathway involves betaine-homocysteine methyltransferase and requires TMG as a cofactor. Betaine is thus involved in the synthesis of many biologically important molecules, and may be even more important in situations where the major pathway for the regeneration of methionine from homocysteine has been compromised by genetic polymorphisms.
TMG in agriculture and aquaculture
TMG supplementation decreases the amount of adipose tissue in pigs; however, research in human subjects has shown no effect on body weight, body composition, or resting energy expenditure, but only on muscle strength (2,5 gr/die).
TMG in the human diet
|Food||TMG per 100g|
|Wheat bran||360 mg|
|Lamb's quarters||332 mg|
Although TMG supplementation decreases the amount of adipose tissue in pigs, research on human subjects has shown no effect on body weight, body composition, or resting energy expenditure when used in conjunction with a hypoenergetic diet. The Food and Drug Administration of the United States approved anhydrous trimethylglycine (also known by the brand name Cystadane) for the treatment of homocystinuria, a disease caused by abnormally high homocysteine levels at birth.
TMG supplementation may cause diarrhea, stomach upset, or nausea. Obese persons or those with kidney disease supplementing with TMG, folic acid, and vitamin B6 can experience an increase in total cholesterol levels.
Other uses: PCR
Trimethylglycine can act as an adjuvant of the polymerase chain reaction (PCR) process, and other DNA polymerase-based assays such as DNA sequencing. By an unknown mechanism, it aids in the prevention of secondary structures in the DNA molecules, and prevents 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 has been determined under experiment that it is best used at a final concentration of 1M.
TMG is sometimes used as a treatment for depression, as it can increase S-adenosylmethionine (SAMe) by remethylating homocysteine. SAMe has been shown to work as a nonspecific antidepressant in several studies.
IEX Ion Exchange Chromatography
In the book from Amersham Biosciences/GE Healthcare, Ion Exchange Chromatography & Chromatofocusing - Principles and Methods, page48. "Zwitterionic additives such as betaine can prevent precipitation and can be used at high concentrations without interfering with the gradient elution"
- Hubert Schiweck, Margaret Clarke, Günter Pollach "Sugar” in Ullmann’s Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim.doi:10.1002/14356007.a25_345.pub2
- P. Mäkelä "Agro-industrial uses of glycinebetaine" Sugar Tech 2004 Volume 6, 207-212. doi:10.1007/BF02942500
- Kempf, B.; Bremer, E."Uptake and synthesis of compatible solutes as microbial stress responses to high-osmolality environments" Arch Microbiol. 1998, volume 170, pp. 319-30. doi:10.1074/jbc.M210970200
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- Xue, M. Xie, S. & Cui Y. (2004). Effect of a feeding stimulant on feeding adaptation of gibel carp Carassius auratus gibelio (Bloch), fed diets with replacement of fish meal by meat and bone meal. Aquaculture Research, 35: 473-482.
- Schwab U, Törrönen A, Toppinen L, et al. (November 2002). "Betaine supplementation decreases plasma homocysteine concentrations but does not affect body weight, body composition, or resting energy expenditure in human subjects". Am. J. Clin. Nutr. 76 (5): 961–7. PMID 12399266.
- Holm PI, Ueland PM, Vollset SE, et al. (February 2005). "Betaine and folate status as cooperative determinants of plasma homocysteine in humans". Arterioscler. Thromb. Vasc. Biol. 25 (2): 379–85. doi:10.1161/01.ATV.0000151283.33976.e6. PMID 15550695.
- Henke W, Herdel K, Jung K, Schnorr D, Loening SA (October 1997). "Betaine improves the PCR amplification of GC-rich DNA sequences.". Nucleic Acids Res 25 (19): 3957–8. doi:10.1093/nar/25.19.3957. PMC 146979. PMID 9380524.
- Angulo P, Lindor KD (2001). "Treatment of nonalcoholic fatty liver: present and emerging therapies". Semin Liver Dis 21 (1): 81–88. doi:10.1055/s-2001-12931. PMID 11296699.
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- "Investigating SAM-e". Geriatric Times. 2001. Retrieved 2006-12-08.
- Kagan, BL; Sultzer, DL; Rosenlicht, N; Gerner, RH (May 1, 1990). "Oral S-adenosylmethionine in depression: a randomized, double-blind, placebo-controlled trial". Am J Psychiatry 147 (5): 591–5. PMID 2183633. Retrieved 2007-02-16.
- Rosenbaum, JF; Fava, M; Falk, WE; Pollack, MH; Cohen, LS; Cohen, BM; Zubenko, GS (May 1990). "The antidepressant potential of oral S-adenosyl-l-methionine". Acta Psychiatrica Scandinavica 81 (5): 432–6. doi:10.1111/j.1600-0447.1990.tb05476.x. PMID 2113347.
- USDA Database for the Choline Content of Common Foods - including the data on choline metabolites, such as betaine, in 434 food items.