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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1fob
Original Entry
Title:
Hydrolase
Compound:
Beta-1,4-galactanase
Mutant:
No
UniProt/Swiss-Prot:
P48842-GANA_ASPAC
EC Class:
3.2.1.89
Other CSA Entries:
Overview of all sites for 1fob
Homologues of 1fob
Entries for UniProt/Swiss-Prot: P48842
Entries for EC: 3.2.1.89
Other Databases:
PDB entry: 1fob
PDBsum entry: 1fob
UniProt/Swiss-Prot: P48842
IntEnz entry: 3.2.1.89
Literature Report:
Introduction:
Asperfillus aculeatus beta-1,4-Galactanase (AAGAL) is an enzyme involved in pectin degradation. It belongs to the glycoside hydrolase family 53 (GH-53) in clan GH-A. It catalyses the endohydrolysis of beta-1,4-linked galactan and type I arabinogalactan to galactose and galactose oligomers.

Galactan and arabinogalactan are components of pectin which attaches to the C4 position of rhamnose. They forms the side-chains of the 'hairy' region of pectin. Degradation and modification of the galatan and arabinogalactan side chain has many industrial applications, so AAGAL has potential industrial uses.
Mechanism:
Glu136 protonates the glycosidic oxygen while Glu246 acts as a nucleophilic to attack the anomeric carbon to form a covalent enzyme-substrate intermediate. The deprotonated Glu136 then activates a water molecule to hydrolyse the covalent enzyme-substrate intermediate. Arg45 hydrogen bonds with Glu246 to ensure that it is deprotonated even at relatively low pH value to allow it to act as a catalytic nucleophile.
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Found by:
Literature reference 
PsiBLAST alignment on 1fhl

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ARGA 45 61Sidechain
ElectrostaticResidue
It hydrogen bonds with Glu 246 and alters the pKa of Glu 246 to keep it deprotonated even at relatively low pH value to allow it to act as a nucleophile to attack the anomeric carbon of the glycosidic bond.
Evidence from paper Evidence concerns Evidence type
PubMed ID 12484750 Current protein Residue is positioned appropriately

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
GLUA 136 152Sidechain
Acid/baseSubstrate
It protonates the oxygen atom of the glycosidic bond. It deprotonates and activates a water molecule to allow it to hydrolyse the enzyme-substrate complex to regenerate the enzyme.
Evidence from paper Evidence concerns Evidence type
PubMed ID 12484750 Current protein Structural similarity to homologue of known mechanism
PubMed ID 12484750 Current protein Conservation of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
GLUA 246 262Sidechain
NucleophileSubstrate
It acts as a nucleophile to attack the anomeric carbon of the glycosidic bond to form an enzyme-substrate intermediate.
Evidence from paper Evidence concerns Evidence type
PubMed ID 12484750 Current protein Conservation of residue
PubMed ID 12484750 Current protein Structural similarity to homologue of known mechanism
References:
1
Aspergillus aculeatus beta-1,4-galactanase: substrate recognition and relations to other glycoside hydrolases in clan GH-A.
C. Ryttersgaard and L. Lo Leggio and P. M. Coutinho and B. Henrissat and S. Larsen
Biochemistry 41, (51) 15135-43, (2002).
12484750
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