GLYCYL-PROLINE IN URINE OF HUMANS WITH BONE DISEASE

Abstract

An unknown ninhydrin-reacting substance has been found in the urine of three human subjects with rickets. A sample of the substance separated from urine by elution chromatography was hydrolyzed in acid, and equimolar amounts of glycine and proline were released. The DNP reaction applied to the substance resulted in DNP-glycine and free proline. The isolated unknown substance and glycyl-L-proline cochromatographed and coelectrophoresed in a number of solvent and buffer systems. The substance was therefore identified as glycyl-proline.Glycyl-proline is apparently excreted from plasma into urine; it is poorly absorbed by the kidney and its transport is independent of either the glycine or the L-proline transport mechanisms.Glycyl-proline was not excreted by normal subjects. It was found only in patients with severe active rickets. Glycyl-proline excretion paralleled that of total bound hydroxyproline, both diminishing as the rickets healed. Bone collagen appears to be the likely source for glycyl-proline in these patients.