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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:
1) protein modification; protein glycosylation; N-glycosylation
2) maturation of Asn-linked oligosaccharides
3) trims a single alpha-1,2-linked mannose residue from Man(9)GlcNAc(2) to produce Man(8)GlcNAc(2)
4) only product is Man(8)GlcNAc(2) isomer B, the form lacking the middle-arm terminal alpha 1,2-mannose
5) glycoprotein quality control (putative)
6) targets misfolded glycoproteins for degradation
7) 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
Note:
- uncertain whether Met-1 or Met-37 is the initiator
General
hydrolase
membrane protein
Properties
SIZE: entity length = 699 aa
MW = 80 kD
COMPARTMENT: endoplasmic reticulum
MOTIF: proline-rich region
SITE: 39-45
MOTIF: proline residue (SEVERAL)
transmembrane domain {85-105}
glutamate residue {E330}
aspartate residue {D463}
cysteine residue {C527}
MODIFICATION: cysteine residue {C556}
cysteine residue {C556}
MODIFICATION: cysteine residue {C527}
glutamate residue {E599}
Database Correlations
OMIM correlations
UniProt Q9UKM7
Pfam PF01532
Entrez Gene 11253
Kegg hsa:11253
ENZYME 3.2.1.113
References
UniProt :accession Q9UKM7