Glucosylceramidase is a lysosomal enzyme that cleaves the beta-glucosidic linkage of glucosylceramide, an intermediate in glycolipid metabolism. The mature enzyme has 497 amino acids with a molecular weight of 62 kDa. Glycosylation occurs at four of five N-glycosylation sites and is essential for the trafficking and activity of the enzyme. The enzyme is activated in lysosomes by saposin C, although the mechanism of activation is not well understood. 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. Symptoms of Gaucher disease may include enlarged spleen and liver, liver malfunction, skeletal disorders and bone lesions, severe neurologic complications, swelling of lymph nodes, anemia, low blood platelets and yellow fatty deposits on the white of the eye. Currently, enzyme replacement therapy is used to treat patients with the disease.