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Catalytic Site Atlas Search Results
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Catalytic Site Atlas

CSA LITERATURE entry for 1ga8

E.C. namelipopolysaccharide 3-alpha-galactosyltransferase
SpeciesNeisseria meningitidis ()
E.C. Number (IntEnz) 2.4.1.44
CSA Homologues of 1ga8There are 11 Homologs
CSA Entries With UniProtID
CSA Entries With EC Number 2.4.1.44
PDBe Entry 1ga8
PDBSum Entry 1ga8
MACiE Entry 1ga8

Literature Report

IntroductionLipo-polysaccharide galactosyl transferase (LGTC) is a retaining glycosyl transferase which catalyses the transfer of alpha-D-galactose to a terminal lactose during the synthesis of lipo-polysaccharides with retention of stereochemistry at the anomeric carbon. The enzyme held at the surface of the bacterial plasma membrane through electrostatic interaction between basic residues and phospho-lipids and interactions between hydrophobic regions.
MechansimInsufficient experimental evidence exists to assign one out of several possible mechanisms for the reaction of LGTC. Structural data and comparisons to similar enzymes suggests a double displacement reaction, while computer modelling favours front side Sni attack. The first mechanism requires Gln189 to act as a nucleophile at the anomeric carbon, forming an enzyme-substrate imidic ester intermediate which is then attacked by the 4-OH group of the acceptor sugar. The second proposed mechanism does not require a catalytic residue and instead employs conformational contortion within the active site to correctly align the reactants.
Reaction

Catalytic Sites for 1ga8

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GlnA189189macie:sideChainExperimental evidence has suggested that Gln189 uses its side chain nitrogen as a nucleophile at the anomeric carbon of the alpha-D-galactose substrate. The enzyme-substrate imidic ester intermediate is then attacked by the 4-OH of the acceptor lactose, forming the product with retention of stereochemistry. However, no intermediate has been observed for this enzyme.
AspA188188macie:sideChainThe residue's side chain stabilises the transition state.
AspA130130macie:sideChainThe residue's side chain stabilises the transition state.

Literature References

Notes:
Persson K
Crystal structure of the retaining galactosyltransferase LgtC from Neisseria meningitidis in complex with donor and acceptor sugar analogs.
Nat Struct Biol 2001 8 166-175
PubMed: 11175908
Tvaroska I.
Molecular modeling insights into the catalytic mechanism of the retaining galactosyltransferase LgtC.
Carbohydr Res 2004 339 1007-1014
PubMed: 15010308
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