Molecular Characterization, Regioselective and Synergistic Action of First Recombinant Type III α-L-arabinofuranosidase of Family 43 Glycoside Hydrolase (PsGH43_12) from Pseudopedobacter saltans.

α-L-Arabinofuranosidase (PsGH43_12) of family 43 glycoside hydrolase and subfamily 12 from Pseudopedobacter saltans was cloned, over-expressed and biochemically characterized. PsGH43_12 displayed molecular mass, ~ 65 kDa. It exhibited activity in pH (5-9) and temperature range (35-55 °C) with maxima at pH 6.5 and 50 °C. PsGH43_12 gave 88.7 U/mg specific activity against rye arabinoxylan and 78.9 U/mg against wheat arabinoxylan. PsGH43_12 displayed Km and Vmax, 3.02 mg/ml and 103 µmole/min/mg, respectively, against rye arabinoxylan and 2.17 mM and 100.7 µmole/min/mg, respectively, against pNP-α-L-arabinofuranoside. 10 mM Mg2+ or Ca2+ ions enhanced PsGH43_12 activity by 54% or 33%, respectively. PsGH43_12 hydrolyzed rye arabinoxylan and released only L-arabinosyl moiety as main product, confirming its specificity towards α-L-arabinofuranoside. The regioselective analysis by NMR showed that PsGH43_12 belongs to type III α-L-arabinofuranoside. The synergistic behavior of PsGH43_12 in saccharification of mild alkali pretreated finger miller stalk (FMS) along with xylanase (CtXyn11A) from Clostridium thermocellum and xylosidase (BoGH43) from Bacteroides ovatus gave twofold higher total reducing sugar (TRS) yield. TLC analysis of pretreated FMS hydrolysed by CtXyn11A and BoGH43 showed xylooligosaccharides and xylose. Addition of PsGH43_12 to above combination gave mostly xylose and arabinose confirming their synergistic behavior and displaying their applicability in hydrolysis of hemicellulosic biomass.