HUMAN DNASE-I CONTAINS MANNOSE-6-PHOSPHATE AND BINDS THE CATION-INDEPENDENT MANNOSE-6-PHOSPHATE RECEPTOR

DNase I isolated from human urine (hDNase) or expressed in Chinese ham ster ovary (CHO) cells contains mannose-phosphorylated oligosaccharide s. hDNase binds to a column of immobilized cation-independent mannose 6-phosphate receptor, with the strongest binding exhibited by the prot ein bearing diphosphorylated oligosaccharides. The binding is inhibite d by 5 mM mannose 6-phosphate, and can be prevented by prior treatment of hDNase with alkaline phosphatase. Phosphorylated high-mannose olig osaccharides were observed at both sites of glycosylation in hDNase by high-performance liquid chromatography-mass spectrometry of a tryptic digest These results indicate that hDNase, though not an acid hydrola se, may enter the lysosomal trafficking pathway, and may have evolved from a lysosomal enzyme.