Catalyzes the hydrolysis of glycosphingolipids and participates in their degradation in the lysosome. Hydrolysis of terminal, non-reducing alpha-D-galactose residues in alpha-D-galactosides, including galactose oligosaccharides, galactomannans and galactolipids. globoside Gb3Cer (d18:1(4E)) + H2O = a beta-D-Gal-(1->4)-beta-D-Glc-(1<->1)-Cer(d18:1(4E)) + D-galactose globoside Gb3Cer + H2O = beta-D-galactosyl-(1->4)-beta-D-glucosyl-(1<->1)-ceramide + D-galactose Galactosylgalactosylglucosylceramidase activity is stimulated by saposin B and ammonium chloride. Homodimer. Belongs to the glycosyl hydrolase 27 family.