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Catalytic Site Atlas

CSA LITERATURE entry for 1fhl

E.C. namearabinogalactan endo-1,4-beta-galactosidase
SpeciesAspergillus aculeatus ()
E.C. Number (IntEnz) 3.2.1.89
CSA Homologues of 1fhlThere are 43 Homologs
CSA Entries With UniProtID P48842
CSA Entries With EC Number 3.2.1.89
PDBe Entry 1fhl
PDBSum Entry 1fhl
MACiE Entry 1fhl

Literature Report

IntroductionFungal Beta 1-4-galactanase is important in the degradation of pectin as it is able to catalyse the hydrolysis of galactan and arrabinogalactan to galactose monomers. It displays sequence identity with other glycosyl hydrolases from glycosyl hydrolase family 53, which is in glycosyl hydrolase clan A.
MechansimGlu 136 acts as the catalytic acid-base which initially protonates the glycosidic oxygen to allow nucleophilic attack on the anomeric carbon by Glu 246. This forms a covalent glycosyl intermediate which is subsequently hydrolysed by a water molecule activated by Glu 136 to cleave the polysaccharide substrate. A hydrogen bond from Arg 45 keeps Glu 246 in a deprotonated state even at low pH values.
Reaction

Catalytic Sites for 1fhl

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GluA136152macie:sideChainProtonates glycosyl oxygen to facilitate nucleophilic attack on the anomeric carbon resulting in the glycosyl-enzyme intermediate. Then activates water to allow hydrolysis of the intermediate.
GluA246262macie:sideChainAttacks anomeric carbon to form the glycosyl-enzyme intermediate which subsequently is hydrolysed to give the products.
ArgA4561macie:sideChainForms Hydrogen bond to Glu 246 to maintain it in a deprotonated state and allow it to act as a nucleophile even at low pH.

Literature References

Notes:
Ryttersgaard C
Aspergillus aculeatus beta-1,4-galactanase: substrate recognition and relations to other glycoside hydrolases in clan GH-A.
Biochemistry 2002 41 15135-15143
PubMed: 12484750
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