Exoglycosidase that cleaves the single beta-linked mannose residue from the non-reducing end of all N-linked glycoprotein oligosaccharides. Hydrolysis of terminal, non-reducing beta-D-mannose residues in beta-D-mannosides. Optimum pH is 4.5-5. Glycan metabolism; N-glycan degradation. Monomer. Ubiquitous. Detected in pancreas, kidney and placenta, ands at lower levels in liver, lung, brain, heart and muscle. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyl hydrolase 2 family.