An abnormal orosomucoid in the plasma of patients with neoplastic disease.

Abstract

Summary Concentrations of the plasma amino acids were measured by ion-exchange chromatography in 12 normal subjects (Group I), 10 patients with acute leukemia (Group II), and 38 patients with malignant melanoma or metastatic carcinoma of lung, ovary, or colon (Group III). In Groups II and III, the average concentrations of glutamine, alanine, proline, histidine, and arginine were subnormal. During these analyses, an abnormally elevated peak of ninhydrin-reactive material in the region of the chromatogram ordinarily occupied by tryptophan was observed in 75% of the subjects in Groups II and III. However, plasma tryptophan concentrations, measured by the specific method of La Du and Michael, were normal. The material responsible for this peak (“tryptophan-region material”) was isolated by gel-filtration and ion-exchange chromatography. It proved to be a glycoprotein with a molecular weight of 40,000 to 50,000. Its behavior in immunodiffusion, immunoelectrophoresis, and acrylamide gel electrophoresis at pH 8.9 and 4.0, and its amino acid composition, were indistinguishable from those of normal human orosomucoid (α 1 acid glycoprotein). However, in acrylamide gel electrophoresis at pH 2.7, and in content of hexoses, glucosamine, and sialic acid, the tryptophan-region material isolated from patients in Groups II and III differed from normal orosomucoid. Tryptophan-region material is a form of orosomucoid with a normal protein moiety but with multiple abnormalities in the carbohydrate side chains.