Azetidine-2-carboxylic acid contaminated dietary proline as a cause of urinary excretion of 4-amino-2-(S-cysteinyl)butyric acid in patients on oral treatment with a synthetic diet.
Three children with branched-chain ketoaciduria (maple syrup urine disease) were found to excrete an abnormal amino acid when they were on an artificial diet. This substance was identified as 4-amino-2-(S-cysteinyl)butyric acid with the use of column liquid chromatography, gas chromatography--mass spectrometry of various derivatives, and 360 MHz 1H-NMR spectroscopy. The same compound was detected in urine samples from subjects undergoing an oral loading test with L-proline. The chromatographic analysis of commercial proline from two sources indicated that one of the batches was contaminated (less than 1%) with L-azetidine-2-carboxylic acid (the homologue of proline with a four-membered ring). The latter compound is probably metabolized by the human via ring-opening and addition of a cysteine moiety. It is highly probable that the artificial diet given to the patients contained the impure proline and that the L-azetidine-2-carboxylic acid in the proline gave rise to the excretion of the 4-amino-2-(S-cysteinyl)butyric acid.
D001383:Azetidinecarboxylic Acid / Q000032:analysis*; D001385:Azetines / Q000032:analysis*; D001711:Biotransformation; D002855:Chromatography, Thin Layer; D004151:Dipeptides / Q000652:urine*; D005260:Female; D005506:Food Contamination; D005526:Food, Formulated / Q000032:analysis*; D006801:Humans; D007223:Infant; D008297:Male; D008375:Maple Syrup Urine Disease / Q000178:diet therapy / Q000652:urine*; D011392:Proline / Q000032:analysis*
D001385:Azetines; D004151:Dipeptides; D001383:Azetidinecarboxylic Acid; C039712:4-amino-2-(S-cysteinyl)butyric acid; D011392:Proline