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. Glycan metabolism; N-glycan degradation. Monomer. Detected in kidney (at protein level) (PubMed:8424779). Highest expression is found in thyroid tissue. The amount of transcript is significantly higher in normal tissues than in tissues affected by the disease (PubMed:7876128). The N-terminus is blocked. N-glycosylated. Defects in MANBA cause beta-mannosidosis, a severe disorder that affects peripheral and central nervous system myelin resulting in tremor, nystagmus, ataxia and early death. The primary storage products associated with the enzyme deficiency are the trisaccharide Man-beta-1-4-GlcNAc-beta-1-4-GlcNAc and the disaccharide Man-beta-1-4-GlcNAc. Belongs to the glycosyl hydrolase 2 family.