Biosynthesis of carnitine and 4-N-trimethylaminobutyrate from 6-N-trimethyl-lysine.
The conversion of 6-N-[Me-(14)C]trimethyl-lysine into carnitine and 4-N-trimethylaminobutyrate (butyrobetaine) was demonstrated in rats kept on a lysine-deficient diet. After the rats were given [(14)C]trimethyl-lysine for 4 days, a total of 17% of the injected label was recovered as carnitine from carcass and urine extracts. Another 8% of the trimethyl-lysine label was converted into 4-N-trimethylaminobutyrate, most of which was recovered from the urine. The conversion of trimethyl-lysine into the above two metabolites supports the pathway of carnitine biosynthesis as lysine+methionine --> 6-N-trimethyl-lysine --> 4-N-trimethylaminobutyrate --> carnitine. In addition, three other metabolites representing 2% of the injected dose were recovered. Only an insignificant portion of the label was recovered as free trimethyl-lysine from the carcass, whereas 22% of the injected label was recovered in the urine. A relatively low specific radioactivity in carnitine was found when 5-N-[Me-(14)C]trimethylaminopentanoate and 6-N-[Me-(14)C]trimethylaminohexanoate were administered to rats in amounts similar to the [(14)C]trimethyl-lysine, suggesting that they were not free intermediates.
D000613:Aminobutyrates / Q000652:urine; D000818:Animals; D001622:Betaine / Q000096:biosynthesis*; D002087:Butyrates / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002331:Carnitine / Q000096:biosynthesis*; D002845:Chromatography; D002855:Chromatography, Thin Layer; D008239:Lysine / Q000378:metabolism* / Q000652:urine; D008697:Methane / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051381:Rats
D000613:Aminobutyrates; D002087:Butyrates; D002250:Carbon Radioisotopes; D001622:Betaine; D008715:Methionine; D008239:Lysine; D008697:Methane; D002331:Carnitine