Betaine is a quaternary ammonium zwitterion, extensively present in animals, plants and microorganisms. It also forms a good dietary source as it is found in wheat, spinach, shellfish and sugar beets. Betaine is a methyl derivative of the amino acid glycine. It is known by different names such as trimethylglycine, glycine betaine, lycine and oxyneurine.
Apart from betaine taking part in transmethylation, it acts as an organic osmolyte in protecting cells under stress. This is being significantly observed in plants and microorganisms. Betaine is also known to increase the levels of S-adenosylmethionine and thus this might reduce the effects of hepatic steatosis.
End-product of oxidative metabolism of choline, betaine is a general methyl donor, in particular in a minor pathway of methionine biosynthesis. It is used to treat homocystinuria, which is a defect in the major pathway of methionine biosynthesis.