Responsible for addition of first and second mannose residues to the outer chain of core N-linked polysaccharides and to O-linked mannotriose. Implicated in late Golgi modifications. Protein modification; protein glycosylation. Interacts with SVP26. Golgi localization depends on SVP26. Glycosylated. Present with 11400 molecules/cell in log phase SD medium. Belongs to the MNN1/MNT family.