spacer
View the latest EBI news stories and important announcements...
more

spacer
Search The CSA
PDB ID
UNIPROT ID
EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1apy

E.C. nameN4-(beta-N-acetylglucosaminyl)-L-asparaginase
SpeciesHomo sapiens (Human)
E.C. Number (IntEnz) 3.5.1.26
CSA Homologues of 1apyThere are 22 Homologs
CSA Entries With UniProtID P20933
CSA Entries With EC Number 3.5.1.26
PDBe Entry 1apy
PDBSum Entry 1apy
MACiE Entry M0266

Literature Report

IntroductionAspartylglucosylaminidase hydrolyses the bonds connecting N-linked oligosaccharides to free (not peptide bonded) asparagine residues. This is an important lysosomal function.
MechansimThe sugar-asparagine substrate binds in the active site pocket, and is attacked by the hydroxyl group of an N-terminal threonine, Thr 183 (1apy numbering). The N-terminal amino group acts as a base in extracting the threonine's O-gamma proton allowing it to attack the substrate carbonyl group. The catalytic properties of Thr 183 are modified by Thr 201, which interacts with the Thr 183 O-gamma, and by Ser 49, which interacts with the Thr 183 alpha amino group. The tetrahedral intermediate that results from the nucleophilic attack is stabilised by an oxyanion hole composed of the side chain of Thr 234 and the backbone NH of Gly 235. Collapse of the tetrahedral intermediate with protonation of the departing amino group by the alpha amino group of Thr 183 generates an acyl-enzyme intermediate. This is then hydrolysed by a water molecule that is deprotonated by the alpha amino group of Thr 183.
Reaction

Catalytic Sites for 1apy

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA4972macie:sideChainForms a hydrogen bond with the alpha amino group of Thr 183 and modifies the catalytic properties of Thr 183.
ThrB201224macie:sideChainSide chain OH interacts with the O-gamma of Thr 183, modifying the catalytic properties of Thr 183.
ThrB234257macie:sideChainSide chain OH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
ThrB183206macie:sideChainSide chain hydroxyl acts as a nucleophile to attack the amide carbonyl of the N-glycosidic bond. Alpha amino group acts as a base to deprotonate the side chain hydroxyl to allow the nucleophilic attack. It also protonates the departing amine leaving group of the sugar, and later deprotonates a water molecule during hydrolysis of the acyl enzyme intermediate.
ThrB183206macie:mainChainAmideSide chain hydroxyl acts as a nucleophile to attack the amide carbonyl of the N-glycosidic bond. Alpha amino group acts as a base to deprotonate the side chain hydroxyl to allow the nucleophilic attack. It also protonates the departing amine leaving group of the sugar, and later deprotonates a water molecule during hydrolysis of the acyl enzyme intermediate.
GlyB235258macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerC4972macie:sideChainForms a hydrogen bond with the alpha amino group of Thr 183 and modifies the catalytic properties of Thr 183.
ThrD201224macie:sideChainSide chain OH interacts with the O-gamma of Thr 183, modifying the catalytic properties of Thr 183.
ThrD234257macie:sideChainSide chain OH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
ThrD183206macie:sideChainSide chain hydroxyl acts as a nucleophile to attack the amide carbonyl of the N-glycosidic bond. Alpha amino group acts as a base to deprotonate the side chain hydroxyl to allow the nucleophilic attack. It also protonates the departing amine leaving group of the sugar, and later deprotonates a water molecule during hydrolysis of the acyl enzyme intermediate.
ThrD183206macie:mainChainAmideSide chain hydroxyl acts as a nucleophile to attack the amide carbonyl of the N-glycosidic bond. Alpha amino group acts as a base to deprotonate the side chain hydroxyl to allow the nucleophilic attack. It also protonates the departing amine leaving group of the sugar, and later deprotonates a water molecule during hydrolysis of the acyl enzyme intermediate.
GlyD235258macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Literature References

Notes:Aspartylglucosylaminidase is synthesised as a precursor protein which is activated by proteolytic cleavage between Asp 182 and Thr 183 to generate the required N-terminal threonine residue. The cleavage generates the alpha and beta subunits of the (alpha)2(beta)2 heterotetramer. The cleavage event is thought to be autocatalytic, and many of the residues involved in the normal glucosylaminidase are believed to be involved in the autocatalytic reaction. The Thr 183 side chain, for example, functions as a nucleophile in both. See ref pubmed ID 14616088 for a discussion.
Tikkanen R
Functional analyses of active site residues of human lysosomal aspartylglucosaminidase: implications for catalytic mechanism and autocatalytic activation.
EMBO J 1996 15 2954-2960
PubMed: 8670796
Fisher KJ
Post-translational processing and Thr-206 are required for glycosylasparaginase activity.
FEBS Lett 1993 323 271-275
PubMed: 8500622
Oinonen C
Three-dimensional structure of human lysosomal aspartylglucosaminidase.
Nat Struct Biol 1995 2 1102-1108
PubMed: 8846222
Saarela J
Autoproteolytic activation of human aspartylglucosaminidase.
Biochem J 2004 378 363-371
PubMed: 14616088
spacer
spacer