Characterization and functional analysis of two novel thermotolerant α-L-arabinofuranosidases belonging to glycoside hydrolase family 51 from Thielavia terrestris and family 62 from Eupenicillium parvum.

Arabinofuranose substitutions on xylan are known to interfere with enzymatic hydrolysis of this primary hemicellulose. In this work, two novel α-L-arabinofuranosidases (ABFs), TtABF51A from Thielavia terrestris and EpABF62C from Eupenicillium parvum, were characterized and functionally analyzed. From sequences analyses, TtABF51A and EpABF62C belong to glycoside hydrolase (GH) families 51 and 62, respectively. Recombinant TtABF51A showed high activity on 4-nitrophenyl-α-L-arabinofuranoside (83.39 U/mg), low-viscosity wheat arabinoxylan (WAX, 39.66 U/mg), high-viscosity rye arabinoxylan (RAX, 32.24 U/mg), and sugarbeet arabinan (25.69 U/mg), while EpABF62C preferred to degrade arabinoxylan. For EpABF62C, the rate of hydrolysis of RAX (94.10 U/mg) was 2.1 times that of WAX (45.46 U/mg). The optimal pH and reaction temperature for the two enzymes was between 4.0 and 4.5 and 65 °C, respectively. Calcium played an important role in the thermal stability of EpABF62C. TtABF51A and EpABF62C showed the highest thermal stabilities at pH 4.5 or 5.0, respectively. At their optimal pHs, TtABF51A and EpABF62C retained greater than 80% of their initial activities after incubation at 55 °C for 96 h or 144 h, respectively.