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The founding member of glycoside hydrolase family 147, BACOVA_05493 from Bacteroides ovatus is a β1,4-galactosidase. The enzyme demonstrates a preference towards longer oligosaccharides and β1,4-galactan, releasing galactopyranose from the oligosaccharide or polysaccharide chain. BACOVA_05493 is unable to hydrolyse β1,4-galactobiose [1].
Kinetics and Mechanism
1NMR analysis of the galactose product released from BACOVA_05493 action on galactotriose revealed cleavage with retention of anomeric stereochemistry [1]. The enzyme is believed to operate through a classical Koshland double-displacement mechanism.
Catalytic Residues
Hydrophobic cluster analysis showed that BACOVA_05493 is a member of Clan GH-A. Based on this assumption the catalytic nucleophile and general acid/base residues were proposed as Glu300 and Glu203, respectively. This hypothesis was supported by mutagenesis data showing that the E300A and E203A mutants were catalytically inactive [1].
Three-dimensional structures
Currently there is no crystal structure of any member of GH147, although sequence analysis and hydrophobic cluster analysis predicts a fold of an (α/β)8 barrel.
Family Firsts
First stereochemistry determination
BACOVA_05493 from B. ovatus was shown to have a retaining mechanism [1].
