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ENZYME entry: EC

Accepted Name
Endoplasmic reticulum Man(9)GlcNAc(2) 1,2-alpha-mannosidase.
Reaction catalysed
Man(9)GlcNAc(2)-[protein] + H(2)O <=> Man(8)GlcNAc(2)-[protein] (isomer 8A(1,2,3)B(1,3)) + D-mannopyranose
  • The enzyme, located in the endoplasmic reticulum, primarily trims a single alpha-1,2-linked mannose residue from Man(9)GlcNAc(2) to produce Man(8)GlcNAc(2) isomer 8A(1,2,3)B(1,3) (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)GlcNAc(2).
PRIAM enzyme-specific profiles3.2.1.209
KEGG Ligand Database for Enzyme Nomenclature3.2.1.209
IUBMB Enzyme Nomenclature3.2.1.209
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