Methylation analysis in glycoprotein chemistry. General procedure for quantification of the products of solvolysis of permethylated glycopeptides and glycoproteins

The effect of castanospermine on the oligosaccharide structures of glycoproteins from lymphoma cell lines

The effect of castanospermine on the processing of N-linked oligosaccharides was examined in the parent mouse lymphoma cell line and in a mutant cell line that lacks glucosidase II. When the parent cell line was grown in the presence of castanospermine at 100 micrograms/ml, glucose-containing high-mannose oligosaccharides were obtained that were not found in the absence of inhibitor. These oligosaccharides bound tightly to concanavalin A-Sepharose and were eluted in the same position as oligosaccharides from the mutant cells grown in the absence or presence of the alkaloid. The castanospermine-induced oligosaccharides were characterized by gel filtration on Bio-Gel P-4, by h.p.l.c. analysis, by enzymic digestions and by methylation analysis of [3H]mannose-labelled and [3H]galactose-labelled oligosaccharides. The major oligosaccharide released by endoglucosaminidase H in either parent or mutant cells grown in castanospermine was a Glc3Man7GlcNAc, with smaller amounts of Glc3Man8GlcNAc and Glc3Man9GlcNAc. On the other hand, in the absence of castanospermine the mutant produces mostly Glc2Man7GlcNAc. In addition to the above oligosaccharides, castanospermine stimulated the formation of an endoglucosaminidase H-resistant oligosaccharide in both cell lines. This oligosaccharide was characterized as a Glc2Man5GlcNAc2 (i.e., Glc(1,2)Glc(1,3)Man(1,2)Man(1,2)Man(1,3)[Man(1,6)]Man-GlcNAc-GlcNAc). Castanospermine was tested directly on glucosidase I and glucosidase II in lymphoma cell extracts by using [Glc-3H]Glc3Man9GlcNAc and [Glc-3H]Glc2Man9GlcNAc as substrates. Castanospermine was a potent inhibitor of both activities, but glucosidase I appeared to be more sensitive to inhibition.

Methylation analysis in glycoprotein chemistry: a comparative study of the carbohydrate structures of three hormone-binding glycoproteins from human serum

The structures of the carbohydrate moieties of three hormone-binding glycoproteins from human serum, namely, thyroxine-binding globulin, transcortin, and sex hormone-binding globulin, have been characterised using quantitative g.l.c. of the methylated monosaccharide derivatives obtained after methanolysis of the methylated glycoproteins.

Pregnancy-associated molecular variants of human serum transcortin and thyroxine-binding globulin

Affinity chromatography on immobilised concanavalin A revealed that transcortin and thyroxine-binding globulin isolated from human postpartum serum contained approximately 10% of molecular variants that did not occur in these glycoproteins isolated from normal donor serum (both male and female). The chromatographic behaviour of the pregnancy-associated glycoprotein variants, their monosaccharide compositions, and the results of methylation analysis indicated that these variants contained only triantennary oligosaccharide chains of the N-acetyl-lactosamine type.

Isolation and characterization of glycopeptides of human transcortin

Pronase digestion of human transcortin yielded two major glycopeptides (GID3 and G2D2, in a molar ratio of approx. 1.0 to 1.5) which were isolated by gel and anion-exchange chromatography. Chromatography behaviour, methylation analysis and analytical chromatography on a Con A-Sepharose column suggested that both of the glycopeptides were N-linked asparaginyl oligosaccharides of the N-acetyllactosamine type, G1D3 and G2D2 being triantennary and biantennary isoglycans, respectively. Microheterogeneity in regard to the position of the linkages between sialyl and galactosyl residues occurred in the triantennary and, possibly, in biantennary isoglycans.

Determination of the Structure of four glycopeptides from hen ovalbumin using 360-MHz proton magnetic resonance spectroscopy

Four glycopeptides have been purified by Dowex and Bio-Gel P2 chromatography from Pronase digests of hen ovalbumin. The high-resolution proton magnetic resonance spectra of these glycopeptides and various products of their enzymatic digestion have been obtained at 360 MHz. By use of information derived from the spectra of a number of model compounds, an unambiguous assignment of all C1-H and Man C2-H resonances in the spectra can be made. On this basis structures are proposed for the four glycopeptides which are identical with those structures previously deduced from destructive chemical methods.