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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1dl2

E.C. namemannosyl-oligosaccharide 1,2-alpha-mannosidase
SpeciesSaccharomyces cerevisiae (Baker's yeast)
E.C. Number (IntEnz) 3.2.1.113
CSA Homologues of 1dl2There are 12 Homologs
CSA Entries With UniProtID P32906
CSA Entries With EC Number 3.2.1.113
PDBe Entry 1dl2
PDBSum Entry 1dl2
MACiE Entry M0019

Literature Report

IntroductionClass I alpha-1,2-mannosidases have been conserved throughout eukaryotic evolution for the maturation of N-glycans during glycoprotein biosynthesis. N-glycan formation begins with the transfer of a preformed oligosaccharide precursor, usually Glc3Man9ClcNac2, to nascent polypeptide chains. The oligosaccharide precursor is then trimmed immediately by alpha-glucosidases and alpha-mannosidases in the endoplasmic reticulum or the golgi apparatus. Besides their importance in N-glycan maturation, endoplasmic reticulum and golgi apparatus processing glycosidases and mannosidases also play a role in quality control, ensuring that only correctly folded proteins are transported to their final destination. Trimming of mannose residues in the endoplasmic reticulum acts as a signal to target misfolded glycoproteins for degradation by the proteasome. Mannosyl-oligosaccharide 1,2-alpha-mannosidase is the only alpha-mannosidase in Saccharomyces cerevisae and it removes a single mannose residue from Man(9)(GlcNAc)(2) to form Man(8)(GlcNAc)(2) in the endoplasmic reticulum as do equivalent enzymes in higher organisms. Class I enzymes found in the golgi apparatus remove all four linked alpha-mannose residues.
MechansimThe catalytic acidic residues and the calcium ion required for activity are located in the centre of an (alpha-alpha)7 barrel at the top of a beta-hairpin. The enzyme is an inverting hydrolase, causing an inversion of configuration at C1 of the tenth oligosaccharide residue. The favourite mechanism proposed is as follows: Glu132 acts as a catalytic base and abstracts a proton from water. A hydrogen bond with Arg136 increases the acidity of Glu132. Asp275 is then thought to act as the catalytic acid donating a proton to the leaving group. The calcium does not appear to play a direct role in catalysis but instead in stabilisation.

Catalytic Sites for 1dl2

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
ArgA136136macie:sideChain
GluA435435macie:sideChain
AspA275275macie:sideChain
GluA132132macie:sideChain

Literature References

Notes:
Chang S
Electronic signatures of all four DNA nucleosides in a tunneling gap.
Nano Lett 2010 10 1070-1075
PubMed: 20141183
Rigatelli G
Patent oval foramen transcatheter closure: results of a strategy based on tailoring the device to the specific patient's anatomy.
Cardiol Young 2010 20 144-149
PubMed: 20219151
Balhorn RL
A selective high affinity ligand (SHAL) designed to bind to an over-expressed human antigen on non-Hodgkin's lymphoma also binds to canine B-cell lymphomas.
Vet Immunol Immunopathol 2010 137 235-242
PubMed: 20576295
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