Involved in endoplasmic reticulum-associated degradation (ERAD). Accelerates the glycoprotein ERAD by proteasomes, by catalyzing mannose trimming from Man8GlcNAc2 to Man7GlcNAc2 in the N-glycans. May also participate in mannose trimming from all glycoproteins and not just misfolded ones targeted to ERAD (PubMed:34143952). May have alpha 1,2-mannosidase activity. 4 H2O + N(4)-(alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 9A1,2,3B1,2,3) = 4 beta-D-mannose + N(4)-(alpha-D-Man-(1->3)-[alpha-D-Man-(1->3)-[alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-beta-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 5A1,2) 3 H2O + N(4)-(alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 8A1,2,3B1,3) = 3 beta-D-mannose + N(4)-(alpha-D-Man-(1->3)-[alpha-D-Man-(1->3)-[alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-beta-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 5A1,2) Protein modification; protein glycosylation. Widely expressed. Expressed at higher level in liver, heart and kidney. Slightly increased by endoplasmic reticulum stress. Contains a protease-associated domain of unknown function. N-glycosylated. The knockout mice show largely skewed ratios of homozygous knockout pups versus heterozygous and wild-type pups. However knockout animals do not present with any obvious phenotype, only subtle changes, such as reduced weight of brains and body, as well as significantly increased abundance of circulating Man8GlcNAc2 and Man9GlcNAc2 in the plasma. Belongs to the glycosyl hydrolase 47 family.