Glucosylceramidase that catalyzes, within the lysosomal compartment, the hydrolysis of glucosylceramides/GlcCers (such as beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine) into free ceramides (such as N-acylsphing-4-enine) and glucose. Plays a central role in the degradation of complex lipids and the turnover of cellular membranes. Through the production of ceramides, participates in the PKC-activated salvage pathway of ceramide formation. Catalyzes the glucosylation of cholesterol, through a transglucosylation reaction where glucose is transferred from GlcCer to cholesterol. GlcCer containing mono-unsaturated fatty acids (such as beta-D-glucosyl-N-(9Z-octadecenoyl)-sphing-4-enine) are preferred as glucose donors for cholesterol glucosylation when compared with GlcCer containing same chain length of saturated fatty acids (such as beta-D-glucosyl-N-octadecanoyl-sphing-4-enine). Under specific conditions, may alternatively catalyze the reverse reaction, transferring glucose from cholesteryl 3-beta-D-glucoside to ceramide. Can also hydrolyze cholesteryl 3-beta-D-glucoside producing glucose and cholesterol. Catalyzes the hydrolysis of galactosylceramides/GalCers (such as beta-D-galactosyl-(1<->1')-N-acylsphing-4-enine), as well as the transfer of galactose between GalCers and cholesterol in vitro, but with lower activity than with GlcCers. Contrary to GlcCer and GalCer, xylosylceramide/XylCer (such as beta-D-xyosyl-(1<->1')-N-acylsphing-4-enine) is not a good substrate for hydrolysis, however it is a good xylose donor for transxylosylation activity to form cholesteryl 3-beta-D-xyloside. a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + H2O = an N-acylsphing-4-enine + D-glucose a beta-D-galactosyl-(1<->1')-N-acylsphing-4-enine + H2O = an N-acylsphing-4-enine + D-galactose cholesteryl 3-beta-D-glucoside + H2O = cholesterol + D-glucose a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + cholesterol = an N-acylsphing-4-enine + cholesteryl 3-beta-D-glucoside beta-D-glucosyl-N-(9Z-octadecenoyl)-sphing-4E-enine + cholesterol = cholesteryl 3-beta-D-glucoside + N-(9Z-octadecenoyl)-sphing-4-enine beta-D-glucosyl-N-octanoylsphing-4E-enine + cholesterol = cholesteryl 3-beta-D-glucoside + N-octanoylsphing-4-enine beta-D-glucosyl-N-dodecanoylsphing-4-enine + cholesterol = cholesteryl 3-beta-D-glucoside + N-dodecanoylsphing-4-enine beta-D-glucosyl-(1<->1)-N-octadecanoylsphing-4-enine + cholesterol = cholesteryl 3-beta-D-glucoside + N-octadecanoylsphing-4-enine beta-D-glucosyl-(1<->1')-N-(15Z-tetracosenoyl)-sphing-4-enine + cholesterol = cholesteryl 3-beta-D-glucoside + N-(15Z-tetracosenoyl)-sphing-4-enine a beta-D-galactosyl-(1<->1')-N-acylsphing-4-enine + cholesterol = an N-acylsphing-4-enine + cholesteryl 3-beta-D-galactoside 1-(beta-D-galactosyl)-N-dodecanoylsphing-4-enine + cholesterol = cholesteryl 3-beta-D-galactoside + N-dodecanoylsphing-4-enine a beta-D-xylosyl-(1<->1')-N-acylsphing-4-enine + cholesterol = an N-acylsphing-4-enine + cholesteryl 3-beta-D-xyloside beta-D-xylosyl-(1<->1')-N-(9Z-octadecenoyl)-sphing-4-enine + cholesterol = cholesteryl 3-beta-D-xyloside + N-(9Z-octadecenoyl)-sphing-4-enine Steroid metabolism; cholesterol metabolism. Sphingolipid metabolism. Interacts with saposin-C. Interacts with SCARB2. Interacts with TCP1. Interacts with GRN; this interaction prevents aggregation of GBA-SCARB2 complex via interaction with HSPA1A upon stress (By similarity). Interaction with saposin-C promotes membrane association. Targeting to lysosomes occurs through an alternative MPR-independent mechanism via SCARB2. Belongs to the glycosyl hydrolase 30 family.