N6-Trimethyl-lysine metabolism. 3-Hydroxy-N6-trimethyl-lysine and carnitine biosynthesis.
Rats injected with N6-[Me-3H]trimethyl-lysine excrete in the urine five radioactively labelled metabolites. Two of these identified metabolites are carnitine and 4-trimethylammoniobutyrate. A third metabolite, identified as 5-trimethylammoniopentanoate, is not an intermediate in the biosynthesis of carnitine; the fourth and major metabolite, N2-acetyl-N6-trimethyl-lysine, is not a precursor of carnitine. The remaining metabolite (3-hydroxy-N6-trimethyl-lysine) is converted into trimethylammoniobutyrate and carnitine by rat liver slices and into trimethylammoniobutyrate by rat kidney slices. In rat liver and kidney-slice experiments, radioactivity from DL-N6-trimethyl-[1-14C]lysine and DL-N6-trimethyl-[2-14C]lysine was incorporated into N2-acetyl-N6-trimethyl-lysine and 3-hydroxy-N6-trimethyl-lysine, but not into trimethylammoniobutyrate or carnitine. A procedure was devised to purify milligram quantities of 3-hydroxy-N6-trimethyl-lysine from the urine of rats injected chronically with N6-trimethyl-lysine (100 mg/kg body wt. per day). The structure of 3-hydroxy-N6-trimethyl-lysine was confirmed chemically and by nuclear-magnetic-resonance spectrometry [Novak, Swift & Hoppel (1980) Biochem. J. 188, 521--527]. The sequence for carnitine biosynthesis in liver is: N6-trimethyl-lysine leads to 3-hydryxy-N6-trimethyl-lysine leads to leads to 4-trimethylammoniobutyrate leads to carnitine.
D000818:Animals; D002250:Carbon Radioisotopes; D002331:Carnitine / Q000096:biosynthesis*; D055598:Chemical Phenomena; D002621:Chemistry; D002855:Chromatography, Thin Layer; D006901:Hydroxylysine / Q000031:analogs & derivatives* / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism; D008954:Models, Biological; D051381:Rats; D014316:Tritium
C025930:3-hydroxy-N(6)-trimethyl-lysine; D002250:Carbon Radioisotopes; D014316:Tritium; D006901:Hydroxylysine; C003712:trimethyllysine; D008239:Lysine; D002331:Carnitine