GENERATION OF HYDROXYTRIMETHYLLYSINE FROM TRIMETHYLLYSINE LIMITS THE CARNITINE BIOSYNTHESIS IN PREMATURE-INFANTS

epsilon-N-Trimethyl-L-lysine (TML) was given orally for 1 day to two g roups of premature infants. There was no change in the output or plasm a levels of carnitine at a dose of 100 mu mol/day; however, the urinar y TML increased 17-fold. In the second group, administration of 1 mmol TML increased the plasma levels and urinary output of carnitine; the output of TML increased 62-fold. During a search of the metabolites of carnitine biosynthesis by H-1 NMR analysis of urine, only one new res onance (corresponding to the TML) could be identified in both groups. Fast atom bombardment mass spectrometry (FAB-MS) analysis of urine sam ples indicated an increase in TML in the treated patients; no changes were found in the relative abundance of any other precursors. These da ta show that a significant limitation of the conversion of hydroxy-TML to carnitine is not likely; rather, the conversion of TML to hydroxy- TML is regulatory in neonatal carnitine biosynthesis.