Structural studies of the carbohydrate moieties of rat kidney gamma-glutamyltranspeptidase. An extremely heterogeneous pattern enriched with nonreducing terminal N-acetylglucosamine residues

Abstract

The carbohydrate moieties of gamma-glutamyltranspeptidase purified from rat kidney were released as oligosaccharides by hydrazinolysis. Fractionation of the oligosaccharide mixture by paper electrophoresis and Bi-Gel P-4 column chromatography and structural study of each component by sequential exoglycosidase digestion in combination with methylation analysis and periodate oxidation have revealed that it is composed of 23 neutral oligosaccharides, monosialyl derivatives of 67 oligosaccharides, disialyl derivatives of 62 oligosaccharides, and trisialyl derivatives of 5 oligosaccharides. The neutral oligosaccharides are either high mannose type or biantennary complex type, and the acidic oligosaccharides are bi-, tri-, and tetranntennary complex type sugar chains. Most of the complex type sugar chains contain an N-acetylglucosamine residue at the C-4 position of the beta-mannosyl residue of their trimannosyl core. Another characteristic feature of these complex type sugar chains is that they are enriched with nonreducing terminal beta-N-acetylglucosamine residues.