endoplasmic reticulum mannosyl-oligosaccharide 1,2-alpha-mannosidase; ER alpha-1,2-mannosidase; ER mannosidase 1; ERman1; man9GlcNAc2-specific-processing alpha-mannosidase; mannosidase alpha class 1B member 1 (MAN1B1)

Function

• protein modification; protein glycosylation; N-glycosylation
• maturation of Asn-linked oligosaccharides
• trims a single alpha-1,2-linked mannose residue from Man(9)GlcNAc(2) to produce Man(8)GlcNAc(2)
• only product is Man(8)GlcNAc(2) isomer B, the form lacking the middle-arm terminal alpha 1,2-mannose
• glycoprotein quality control (putative)
• targets misfolded glycoproteins for degradation
• inhibited by both 1-deoxymannojirimycin & kifunensine

Cofactor: Ca+2

Kinetic parameters:

• KM=0.4 mM for man9GlcNAc2
• pH dependence:
• optimum pH is between 6.5 & 6.9

Compartment

• endoplasmic reticulum membrane
• single-pass type 2 membrane protein

Expression

widely expressed

Pathology

• defects in MAN1B1 are the cause of mental retardation autosomal recessive type 15

Notes

• uncertain whether Met-1 or Met-37 is the initiator

More general terms

• hydrolase
• membrane protein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=11253
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:11253
• OMIM: https://mirror.omim.org/entry/604346
• OMIM: https://mirror.omim.org/entry/614202
• UniProt: http://www.uniprot.org/uniprot/Q9UKM7.html