Studies on the catabolism of glycated haemoglobin: Glycated globin is not a substrate for the glucosyl-galactosyl-hydroxylysine glucosidase but for a peptidase activity present in rat kidney and spleen.

Rat kidney and spleen glucosyl-galactosyl-hydroxylysine glucosidase (EC.3.2.1.107) whose specificity for the hydroxylysine-linked disaccharide units present in collagens depends upon the substrate's free amino group was tested for its glycosidase activity on the ketoamine form of glycated [(14)C]Glc-Globin. The most stable preparations of the enzyme from normal and diabetic rat tissues, partially purified by ultracentrifugation and ammonium sulphate fractionation, were used. These glucosidase preparations did not release any significant amount of radioactive neutral hexose. But a radioactive glycopeptide of about 1,400 Da was released from [(14)C]Glc-Globin at a pH optimum of 4.0. It appears to be released by a peptidase activity present in the kidney and spleen of normal and diabetic rats.