Sulfur-containing amino acids in the plasma and urine of homocystinurics

Abstract The concentrations of several sulfur-containing amino acids were measured in the blood plasma and urine of 7 children with homocystinuria. By treating fresh blood and urine with iodoacetic acid, which converts the easily oxidized homocysteine to the stable derivative S -carboxymethylhomocysteine, it was possible to show that homocysteine is routinely present in the blood and freshly voided urine of homocystinurics. A considerable variation was found in the plasma concentrations of methionine and of homocysteine plus homocystine among the patients studied. S -Adenosylhomocysteine was isolated in pure form from the urine of one homocystinuric child, and appeared to be present in the urines of 3 other homocystinurics. In addition, two as yet unidentified homocysteine-containing disulfide compounds were isolated from the urines of two homocystinuric children, and appeared to be present in the urines of four other patients. 5-Amino-4-imidazolecarboxamide-5/- S -homocysteinylriboside and homolanthionine were isolated from the urines of two homocystinuric patients, and they appeared to be regularly excreted in this disorder. Homotaurine could not be detected in homocystinuric urine. It is possible that one or more of the unusual sulfur-containing metabolites of methionine present in patients with homocystinuria may play a role in causing the unusual pathological manifestations of this disease.