Effect of galactosidase enzymes on the glycoproteins of the platelet membrane determined using lectins

Abstract

Eight lectins specific for different 125I-labelled carbohydrates were employed to study the effect of the neuraminidase, alpha-galactosidase, and beta-galactosidase enzymes on the glycoproteins and terminal carbohydrates of platelet membranes.Neuraminidase was seen to cause a decrease in molecular weight, as measured by polyacrylamide gradient electrophoresis, in glycoproteins IIb and III; this was apparently due to an almost 50% decrease in N-acetyl-D-glucosamine terminals.At the same time, new D-mannose and D-galactose terminals became accessible to the lectins.The alpha- and beta-galactosidases did not seem to affect the molecular weight of the glycoproteins appreciably, though the N-acetyl-D-glucosamine terminals decreased and D-galactose debris increased; differences were observed in the effects of both enzymes.The results confirm that N-acetyl-D-glucosamine, D-mannose and D-galactose are the most abundant membrane carbohydrates and suggest that the first is found as a terminal whereas the others must also be located in the internal zones of the glycoproteins.