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

Abstract

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\x=req-\ 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 \g=b\-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 \ g = b \ \ x = r e q -\ mercaptolactate disulfide. The latter was isolated (compound 2) and its structure was confirmed by degradation, mass spectrometry, and partial synthesis (Fig 1). Materials and MethodsInfrared (IR) spectra were measured on a Perkin-Elmer Model 237 spectrophotometer. All samples were examined as potassium bromac disks.Mass spectra were obtained on a Varían MAT model SM 1 double focussing mass spectrometer. Samples were admitted by direct insertion into the ion source. This instrument features a watercooled shield to prevent excessive heating of the sample from the hot ionization chamber walls. This leads to a much closer control over the temperature of the material being examined with consequent reduction of thermal decomposition of unstable molecules. The following running conditions were applied throughout the study: electron energy, 70 volts; electron current, 300 microamperes; source temperature, 180 C; sample vaporization temperature, 80 to 100 C; and pre¬ cision of mass measurement (limited by the low intensity of most of the ions), ± 10 ppm with the resolving power set to 2,000.Gas-liquid chromatography (GC) was car¬ ried out on a Perkin-Elmer F 11 Chromatograph fitted with dual hydrogen flame ionization de¬ tectors. The column employed was 18 ft 5 mm stainless steel packed with 15% polyethylene glycol succinate (PEGS) on "Chromosorb" P. The carrier gas (nitrogen) flow rate was 30 ml/ min and the column temperature was linearly programmed from 90 to 160 C at 5 C/min. Injec¬ tion block temperature was 200 C. Fig 1.-Structural formulae of derivatives and frag¬ ments of 3-mercaptolactate-cysteine disulfide observed during mass spectrometry. Formula 5, X = COCF corresponds to peak A in Fig 4 to 6; X = H corresponds to peak C in Fig 4 to 6. Formula 6, X = COCFs cor¬ responds to peak B' in Fig 10 and X -H corresponds to D' in Fig 10.

Rhodanese-Fold Containing Proteins in Humans: Not Just Key Players in Sulfur Trafficking

“…MPST is involved in H 2 S production in the brain, kidney, and liver at the mitochondrial level [ 58 ]. From a pathophysiological point of view, an MPST deficiency in humans is associated to a rare syndrome called mercaptolactate-cysteine disulfiduria, characterized by mental disorder and a specific form of disulfiduria [ 59 , 60 , 61 ].…”

Cysteine Aminotransferase (CAT): A Pivotal Sponsor in Metabolic Remodeling and an Ally of 3-Mercaptopyruvate Sulfurtransferase (MST) in Cancer

“…Furthermore, MST is involved in the biosynthesis of enzymatic cofactors, vitamins, and sulfur-containing nucleic acids [ 37 ]. The relevant role of MST in human physiology is highlighted in individuals with mercaptolactate-cysteine disulfiduria (MCDU) due to MPST mutations, who present a deficient methionine cycle and sulfur amino acid metabolism in erythrocytes, and excrete elevated levels of mercaptolactate-cysteine disulfide in the urine [ 122 , 123 , 124 ]. MST deficiency leads to a shift in mercaptopyruvate degradation towards lactate dehydrogenase, producing mercaptolactate [ 35 ].…”

Mental Deficiency and a New Aminoaciduria

“…Psychological.-The over-all mental age was found to be4 years 1 month, with an IQ of 22 on the Stanford-Binet test. The basal age was at the 3 year level with the ceiling at age 7.…”

“…It was then trans¬ ferred to a small tube, sealed, and sent to Dr. Crawhall's laboratory in London for the further purification and study which finally resulted in its identification. 4 Loading Studies.-When the patient was maintained on a regular institutional diet, he excreted approximately 300 mg of the unknown per 24 hours. When he was given an oral cysteine load (100 mg/ kg body weight), urinary excretion of the unknown increased to 2.9 gm/day while there was no significant change in the excretion of the other amino acids.…”