2-Mercaptoethanesulfonate-cysteine disulfide excretion following the administration of 2-mercaptoethanesulfonate--a pitfall in the diagnosis of sulfite oxidase deficiency.

In the urine of a neonate with respiratory insufficiency and convulsions a positive sulfite reaction was found, which is suggestive of sulfite oxidase deficiency. The nitroprusside reaction also was positive. More detailed investigations showed that both tests were positive due to the administration of 2-mercaptoethanesulfonate, a mucolytic drug. The patient's urine contained an acidic amino acid with a column chromatographic behaviour like S-sulfocysteine. The high-voltage electrophoretic mobility was slightly different. This compound was isolated from the urine and identified as the mixed disulfide of 2-mercaptoethanesulfonate and cysteine. Its identity was proven with field desorption mass spectrometry, a technique which is suitable for the analysis of sulfonic acid derivatives.

Chromatographic determination and mass spectrometric identification of gamma-glutamylphenylalanine, a urinary constituent in phenylketonuria.

The occurrence of gamma-glutamylphenylalanine in the urine of patients with phenylketonuria could be demonstrated using chromatographic techniques and mass spectrometry. Concentrations ranged up to 35 mg/l. Only a weak correlation between the urinary excretion of this compound and phenylalanine was seen. The ages of the patients investigated ranged from 2 weeks to 18 years. The origin of the dipeptide is discussed.

Nepsilon-(beta-Aspartyl)lysinuria in children with various pathological conditions.

The isolation, identification, and quantitative determination of an unusual urinary dipeptide, Nepsilon-(beta-aspartyl)lysine, is described, as well as its synthesis. This compound was observed in children in various disease states, but without any correlation with a particular symptom. Its origin is discussed.