Table 1.
Distribution of the current β-xylosidases in the CAZy database, their catalytic domain fold, their type of catalytic mechanism, and their catalytic residues.
| Family (GH) | Total Number of β-xylosidase Sequences | Clan | Overall Fold of the Catalytic Domain | Catalytic Mechanism † | Nucleophile | General Acid/Base |
|---|---|---|---|---|---|---|
| ‡ 1 | 2 | A | (β/α)8 TIM-barrel | Retention | Glu | Glu |
| 3 | 103 | n.a. # | (β/α)8 TIM-barrel | Retention | Asp | Glu |
| 5 | 1 | A | (β/α)8 TIM-barrel | Retention | Glu | Glu |
| 30 | 4 | A | (β/α)8 TIM-barrel | Retention | Glu | Glu |
| 39 | 24 | A | (β/α)8 TIM-barrel | Retention | Glu | Glu |
| 43 | 96 | F | 5-bladed β-propeller | Inversion | Asp § | Glu |
| 51 | 2 | A | (β/α)8 TIM-barrel | Retention | Glu | Glu |
| 52 | 11 | O | (α/α)6-barrel | Retention | Glu | Asp |
| ‡ 54 | 2 | n.a. # | β-sandwich % | Retention | Glu % | Asp % |
| ‡ 116 | 1 | O | (α/α)6-barrel | Retention | Glu | Asp |
| 120 | 2 | n.a. # | right-handed parallel β-helix | Retention | Asp | Glu |
†: Catalysis by GHs commonly proceeds with either retention or inversion of the substrate’s anomeric carbon configuration. See main text for further information. ‡: It is unknown whether the enzymes from GH1, GH54, and GH116 have β-xylosidase activity on natural substrates. #: Not part of a clan. §: General base; General acid. %: Not assigned in the CAZy database. Data are from the crystal structure of the α-l-arabinofuranosidase from Aspergillus kawachii IFO4308 [38].