Crystal Structures of Glycoside Hydrolase Family 51 α-L-Arabinofuranosidase from Thermotoga maritima

alpha-L-Arabinofuranosidase from the hyperthermophilic bacterium Thermotoga maritima (Tm-AFase) is an extremely thermophilic enzyme belonging to glycoside hydrolase family 51. It can catalyze the transglycosylation of a novel glycosyl donor, 4,6-dimethoxy-1,3,5-triazin-2-yl (DMT)-beta-D-xylopyranoside. In this study we determined the crystal structures of Tm-AFase in substrate-free and complex forms with arabinose and xylose at 1.8-2.3 angstrom resolution to determine the architecture of the substrate binding pocket. Subsite -1 of Tm-AFase is similar to that of alpha-L-arabinofuranosidase from Geobacillus stearothermophilus, but the substrate binding pocket of Tm-AFase is narrower and more hydrophobic. Possible substrate binding modes were investigated by automated docking analysis.