IDENTIFICATION OF N-ACETYL-S-(3-OXO-3-CARBOXY-N-PROPYL)CYSTEINE IN THE URINE OF A PATIENT WITH CYSTATHIONINURIA USING LC APCI-MS/

A new cystathionine metabolite has been identified in the urine of a p atient with cystathioninuria using liquid chromatography-mass spectrom etry with an atmospheric pressure chemical ionization interface system (LC/APCI-MS). By this method a very intense quasi-molecular ion was o bserved a's a base peak of synthetic N-acetyl-S-(3-oxo-3-carboxy-n-pro pyl)cysteine (NAc-OCPC). The quasi-molecular ion [M+H](+) of NAc-OCPC observed in the urine of a patient with cystathioninuria was the same as that of the authentic compound (m/z 264). The retention time and R( f) value on paper chromatography of the synthetic compound were the sa me as those of the urinary compound from the patient with cystathionin uria. From these results, this new cystathionine metabolite was identi fied as N-acetyl-S-(3-oxo-3-carboxy-n-propyl)cysteine.