Table 1 Classification of glycoside hydrolases (GH) family consisting of xylanase
From: A detailed overview of xylanases: an emerging biomolecule for current and future prospective
GH family | Clan | Activities in family | Properties | Mode of action | References | |
|---|---|---|---|---|---|---|
Structure | Functional | |||||
GH 5 | GH-A | endo-β-1,4-Xylanase; β-glucosidase cellulase | Consist of seven amino acid (β/α)8 barrel fold Highly conserved | Largest GH family Substitute on main xylan chain | CNB-Glu CPD-Glu Retaining | |
GH 7 | GH-B | endo-β-1,4-Glucanase | High-molecular weight and low pI β-Jelly roll small substrate-binding site (4 subsite and 1 catalytic site) | Common characteristics with family 10 and 11 | CNB-Glu CPD-Glu Retaining | |
GH 8 | GH-M | Cellulases; chitosanases; lichenases; endo-1,4-β-xylanases | (α/α)6 fold Large substrate-binding cleft | Cold-adapted Break xylan into X3 and X4 Highly active on long-chain XOS | CNB-Asp CPD-Glu Inversion of the anomeric | |
GH 10 Family G | GH-A | endo-1,4-β-Xylanases; endo-1,3-β-xylanases | Low-molecular mass high pI (8–9.5) (α/β)8 barrel fold Small yet numerous (4–5) substrate-binding sites | Attack on aryl β-glycosides and aglyconic bond of X2 and X3, respectively Highly active on short XOS | CNB-Glu CPD-Glu Retaining | Ahmed et al. (2009), Collins et al. (2005), Lombard et al. (2014), Motta et al. (2013) |
GH11 | GH-C | xylanases “true xylanases” (active on xylose substrate) | High MW and lower pI values β-Jelly roll Small size Large substrate-binding clefts (7 subsites) | Attack on aryl β-glycosides and aglyconic bond of X2 and X3, respectively Inactive on aryl cellobiosides High substrate selectivity and catalytic efficiency Wide pH and temperature stability Cold-adapted Highly active on long-chain XOS | CNB-Glu CPD-Glu Retaining | Ahmed et al. (2009), Collins et al. (2005), Lombard et al. (2014), Motta et al. (2013) |
GH 43 | GH-F | β-Xylosidase α-l-Arabinofuranosidase; xylanase | β-Propeller (5 blade) fold Catalytic residue glutamate and aspartate in the center | Debranching and degradation of hemicellulose polymer | CNB-Asp CPD-Glu Inverting single displacement mechanism | Collins et al. (2005), Lombard et al. (2014), Mewis et al. (2016) |