Biosynthesis of Trimethylammonium Compounds in Aquatic Animals: I. Formation of Trimethylamine Oxide and Betaine from C14-labelled Compounds by Lobster (Homarus americanus)

Abstract

The formation of trimethylamine oxide and betaine in lobster has been studied in vivo with radioactive carbon. C14-labelled compounds, tested as possible precursors, were administered to lobsters by injection into the abdominal muscle. Incorporation of the tracer into trimethylamine oxide and betaine, isolated from the whole body, was followed after a metabolic period of 24 and 72 hours.Administration of Na formate-C14, DL-serine-3-C14and glycine-2-C14does not lead to labelling of trimethylamine oxide. L-methionine-methyl-C14was a poor precursor of trimethylamine oxide, compared with choline-methyl-C14. These findings suggest a possible function for choline or a derivative in trimethylamine oxide biosynthesis.It appears that the formation of betaine in lobster takes place by oxidation of choline rather than by methylation of glycine. Choline-methyl-C14was found to be a very good precursor, whereas glycine-2-C14was not converted to betaine.