Glucosylceramidase that catalyzes, within the lysosomal compartment, the hydrolysis of glucosylceramide/GlcCer into free ceramide and glucose. Thereby, it plays a central role in the degradation of complex lipids and the turnover of cellular membranes. Through the production of ceramides,it participates in the PKC-activated salvage pathway of ceramide formation and plays a role in cholesterol metabolism. It may either catalyze the glucosylation of cholesterol, through a transglucosylation reaction that transfers glucose from glucosylceramide to cholesterol. Defects in Glucosylceramidase are the cause of Gaucher disease, also known as glucocerebrosidase deficiency. Gaucher disease is the most prevalent lysosomal storage disease, characterized by accumulation of glucosylceramide in the reticulo-endothelial system. Currently, enzyme replacement therapy is used to treat patients with the disease.