Degrades free oligosaccharides in the vacuole. Hydrolysis of terminal, non-reducing alpha-D-mannose residues in alpha-D-mannosides. Binds 1 zinc ion per subunit. Composed of isoforms with three constituent polypeptides described as [(107 kDa)-n (73 kDa)-(6-n) (31 kDa)-(6-n)], where n is 0-6. The 73 kDa and the 31 kDa polypeptides may be proteolytic derivatives of the 107 kDa polypeptide in the vacuole. Oligomerizes in the cytoplasm and retains its oligomeric form during import into the vacuole. Localizes to the inner surface of the vacuolar membrane. Under nutrient-rich conditions, the protein is delivered to the vacuole by the cytoplasm to vacuole targeting (Cvt) pathway. Under starvation conditions, the protein is localized through autophagy. The N-terminus is blocked. It is not specific for the 1,2-alpha-mannosidic linkage. Present with 319 molecules/cell in log phase SD medium. Belongs to the glycosyl hydrolase 38 family.