[Purification and characterization of alkaline xylanases from Pseudomonas G6-2]

Pseudomonas G6-2 produced two extracellular xylanases, named XynA and XynB. The enzymes were purified by ammonium sulfate fractionation, Sephadex G-100, DEAE-Sephadex, CM-Sephadex and Bio-gel P-10 chromatographies. Both enzymes were indicated to be endoxylanases, which produced oligomers of xylose from xylan and did not hydrolyze it to xylose. They had same temperature optimum(50 degrees C) and different pH optimum(pH 7.0-9.8 for XynA and pH 7.0-8.0 for XynB). At pH 7.6 and 65 degrees C, XynA and XynB possessed the half life of 6 min and 140 min, respectively. Their activities were strongly inhibited by Cu2+, Fe3+, Pb2+, Zn2+ and Hg2+. The results of chemical modification indicated that tryptophan and carboxy group were related to active center.