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ENZYME entry: EC 3.2.1.209

Accepted Name
endoplasmic reticulum Man9GlcNAc2 1,2-alpha-mannosidase.
Reaction catalysed
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) <=> beta-D-mannose + 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)-beta-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 8A1,2,3B1,3)
Comment(s)
  • The enzyme, located in the endoplasmic reticulum, primarily trims a single alpha-1,2-linked mannose residue from Man9GlcNAc2 to produce Man8GlcNAc2 isomer 8A1,2,3B1,3 (the names of the isomers listed here are based on a nomenclature system proposed by Prien et al (pmid:19181540)).
  • The removal of the single mannosyl residue occurs in all eukaryotes as part of the processing of N-glycosylated proteins, and is absolutely essential for further elongation of the outer chain of properly-folded N-glycosylated proteins in yeast.
  • In addition, the enzyme is involved in glycoprotein quality control at the ER quality control compartment (ERQC), helping to target misfolded glycoproteins for degradation.
  • When present at very high concentrations in the ERQC, the enzyme can trim the carbohydrate chain further to Man(5-6)GlcNAc2.
Cross-references
BRENDA3.2.1.209
EC2PDB3.2.1.209
ExplorEnz3.2.1.209
PRIAM enzyme-specific profiles3.2.1.209
KEGG Ligand Database for Enzyme Nomenclature3.2.1.209
IUBMB Enzyme Nomenclature3.2.1.209
IntEnz3.2.1.209
MEDLINEFind literature relating to 3.2.1.209
MetaCyc3.2.1.209
Rhea expert-curated reactions3.2.1.209
UniProtKB/Swiss-Prot
Q9C512, MNS1_ARATH;  Q93Y37, MNS3_ARATH;  

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