Betaine Metabolism

Betaine (or trimethylglycine) is related to choline (trimethylaminoethanol), with the difference that the terminal carboxylic acid group of trimethylglycine has been reduced to a hydroxyl group in choline. Betaine is obtained by humans from foods, either as betaine or choline-containing compounds. The conversion of choline to betaine is a two-step enzymic process, which occurs in the liver and kidney. Choline is first oxidised to betaine aldehyde, a reaction catalysed by the mitochondrial choline oxidase (choline dehydrogenase). In a subsequent step, betaine aldehyde is further oxidised in the mitochondria or cytoplasm to betaine by betaine aldehyde dehydrogenase. Betaine 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. Betaine also plays a role in the manufacture of carnitine and serves to protect the kidneys from damage. Betaine also donates a methyl group to convert homocysteine to methionine in a reaction catalysed by BHMT (Betaine Homocysteine Methyltransferase). Methionine is then converted to SAMe by Methionine Adenosyl Transferase (MAT) using magnesium and adenosine triphosphate as co-factors. The product of demethylation of betaine is dimethylglycine.