Hydrolysis of the glycosidic linkage between oligosaccharides and ceramides of glycosphingolipids, especially b-series polysialogangliosides. an oligoglycosyl-(1->4)-beta-D-glucosyl-(1<->1)-ceramide + H2O = an N-acyl-sphingoid base + an oligoglycosyl-(1->4)-D-glucose Completely inhibited by Hg(2+). Cu(2+) and zinc have no effect on enzyme activity. Lithium, potassium, manganese, Ni(2+), calcium, magnesium and EDTA have no significant effect on enzyme activity. Enzyme requires presence of detergents such as Triton X-100 and Lubrol PX for the hydrolysis of glycosphingolipids. Taurodeoxycholate strongly inhibits the enzyme activity and SDS completely inhibits the enzyme activity. Optimum pH 3.0. Highly stable at acidic pH. Belongs to the glycosyl hydrolase 5 (cellulase A) family.