β-Mercaptolactate-Cysteine Disulfide in the Urine of a Mentally Retarded Patient

A SULFUR-containing amino acid in the urine of a mentally deficient patient, observed by Ampola et al,¹ did not correspond in its chromatographic properties to any previously described amino acid. The patient was born following a brother-sister mating and the mental and physical findings have been described in the previous paper.¹ The method of isolation, purification, and characterization of this amino acid followed by partial synthesis will be described. The amino acid, which was shown to be β-mercaptolactate-cysteine disulfide (compound 1) was isolated from the urine by the methods of preparative column chromatography described in reference 1 and was then in the form of an oil and contained some ninhydrin positive and ninhydrin negative impurities as well as urinary pigments. Intermolecular disulfide exchange of compound 1 can occur, which gives rise to cystine and β-mercaptolactate disulfide. The latter was isolated (compound 2) and its structure was confirmed by