PURIFICATION AND SOME PROPERTIES OF XYLAN-HYDROLYZING ENZYMES FROM ROBILLARDA SP-Y-20

Two endo-1,4-β-d-xylanases (1,4-β-d-xylan xylanohydrolase, EC 3.2.1.8) have been isolated from culture filtrates of Robillarda sp. Y-20 by combinations of isoelectric focusing and Toyopearl HW-50S gel filtration. These enzymes were homogeneous on gel filtration, isoelectric focusing, and polyacrylamide gel electrophoresis with and without sodium dodecyl sulfate (SDS). The molecular weights of the two xylanases (I and II) determined by SDS-polyacrylamide gel electrophoresis were 17,600 and 59,000, respectively. The pI values were 9.7 and 3.5 for xylanase I and II, respectively. Both xylanases had the same optimum pH (4.5-6) and temperature 50°C values and were stable over a wide range of pH values. From kinetic analysis, apparent Vmax and Km values of 225.7 μmol min-1 and 1.25% were obtained for xylanase I, while values of 8.1 μmol min-1 and 0.20% were obtained for xylanase II. Both xylanases attacked xylopentaose and xylotetraose more readily than xylotriose, but did not hydrolyse xylobiose. The end products of xylan and xylooligosaccharide hydrolysis by xylanase I and II showed the presence of xylose, xylobiose, and xylotriose. In the case of xylan, the main product was xylobiose. © 1990.