Difference in the sugar chains of two subunits and of isozymic forms of rat kidney γ-glutamyltranspeptidase

Abstract

A comparative study by gel-permeation chromatographic analysis of oligosaccharides released from the heavy and the light subunits of rat kidney γ-glutamyltranspeptidase has revealed that high-mannose-type sugar chains are found only in the heavy subunit, and the nonsialylated and nonfucosylated biantennary complex-type sugar chains are included only in the light subunit. By the same analysis of the oligosaccharide fractions obtained from four isozymic forms of rat kidney γ-glutamyltranspeptidase, it was found that all these enzymes contain 2 mol of neutral sugar chains but different numbers of acidic sugar chains. The total numbers of sialic acid residues showed a reciprocal relationship to the isoelectric point of each isozymic form, and an increase of 1 mol of sialic acid residue corresponds to a decrease of 0.5 in the value of the isoelectric point.