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Glycoside Hydrolase Family 110
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|Glycoside Hydrolase Family GH110|
|Active site residues||not known|
|CAZy DB link|
This family of glycoside hydrolases was recently discovered following an effort to isolate enzymes for the selective and efficient removal of the terminal α-galactose residue on B antigen for the enzyme conversion of blood group B to universal group O . The activity of several enzymes has been studied and they display narrow substrate specificity for the branched blood group B oligosaccharide (Galα1–3(Fucα1–2)Gal). Interestingly and in contrast to many cases where glycosidases display a higher apparent activity on pNP-substrates than on oligosaccharides, the enzyme from B. fragilis NCTC 9343 (BfGal110A) exhibited a lower activity with pNP-α-Gal (0.3 U/mg) compared to the blood group B substrate (6.6 U/mg). The substrate specificity was remarkably stringent for α-1,3-linked galactose in the branched blood group B structure. The enzyme cleaved neither α4Gal linkages found in P1 and Pk blood group antigens nor the α3Gal linkage in the linear B structure without fucose (the so-called Galili antigen). In a subsequent study Liu et al. have shown the existence of two distinct subfamilies, one subfamily being exclusively active on the branched blood group B structures, whereas the other subfamily contained linkage specific α1,3-galactosidases that act equally well on both branched blood group B and linear α-1,3-Gal structures .
Kinetics and Mechanism
The enzymes of this family are classified as inverting enzymes. The stereochemistry of hydrolysis has been monitored by 1H NMR using p-nitrophenyl α-galactoside as the substrate and B. fragilisBfGal110B as the enzyme. The results showed that the enzyme initially produces β-galactose, i.e. operates with overall inversion of the anomeric configuration, which is in striking contrast to all other known α-galactosidases that use a retaining mechanism (see Glycoside Hydrolase Family 4, Glycoside Hydrolase Family 27, Glycoside Hydrolase Family 36 and Glycoside Hydrolase Family 57) .
- First sterochemistry determination
- B. fragilisBfGal110B by 1H NMR .
- Liu QP, Sulzenbacher G, Yuan H, Bennett EP, Pietz G, Saunders K, Spence J, Nudelman E, Levery SB, White T, Neveu JM, Lane WS, Bourne Y, Olsson ML, Henrissat B, and Clausen H. (2007) Bacterial glycosidases for the production of universal red blood cells. Nat Biotechnol. 25, 454-64. DOI:10.1038/nbt1298 |
- Liu QP, Yuan H, Bennett EP, Levery SB, Nudelman E, Spence J, Pietz G, Saunders K, White T, Olsson ML, Henrissat B, Sulzenbacher G, and Clausen H. (2008) Identification of a GH110 subfamily of alpha 1,3-galactosidases: novel enzymes for removal of the alpha 3Gal xenotransplantation antigen. J Biol Chem. 283, 8545-54. DOI:10.1074/jbc.M709020200 |