Exoglycosidase that cleaves the single beta-linked mannose residue from the non-reducing end of beta-mannosidic oligosaccharides of various complexity and length. Involved in the degradation of polymeric mannan and galactomannan. Releases the terminal mannose residue from mannotriose and is somewaht less active on other mannooligosaccharides. Hydrolysis of terminal, non-reducing beta-D-mannose residues in beta-D-mannosides. Optimum pH is 2.0. Stable from pH 4 to pH 7. Optimum temperature is 70 degrees Celsius. Glycan metabolism; N-glycan degradation. Homodimer. N-glycosylated. Belongs to the glycosyl hydrolase 2 family. Beta-mannosidase A subfamily.