Clinical significance of serum hydroxyproline-containing peptides with special reference to hyproprotein

Serum hydroxyproline-containing peptides were separated into three fractions, i.e. large protein, polypeptide and smaller peptides, by gel filtration on Sephadex G-200. The large protein was presumed to be the Clq subunit of the first component of complement by an immunological analysis. The polypeptide had an electrophoretic mobility corresponding to β-globulin and its molecular weight was estimated between 35 000 and 45 000 by gel filtration analysis. The polypeptide might well be defined as hyproprotein. The molecular weight of smaller peptides was estimated between 1400 and 3000. As compared with the control value, hyproprotein levels were significantly increased in rheumatoid arthritis, systemic lupus erythematosus and chronic liver disease. Clq levels were slightly lowered in rheumatoid arthritis and systemic lupus erythematosus, and were slightly increased in chronic liver disease but were not significant. In all patient groups smaller peptides levels remained in the normal range. These results suggest that serum hyproprotein levels are raised in some fibroproliferative disorders, probably reflecting collagen metabolism.