1998 Volume 64 Issue 5 Pages 787-792
β-Xylosidase was purified from the culture fluid of a bacterium, Bacillus sp. XY-131, by ammonium sulfate precipitation and successive column chromatographies. The final enzyme preparation showed a single protein band on SDS-PAGE. The enzyme's molecular mass was 172kDa as estimated by sucrose density gradient ultracentrifugation and 180kDa as estimated by gel-filtration chromatography. SDS-PAGE suggested that the enzyme molecule was a trimer with a subunit molecular mass of 61kDa. The purified enzyme had a pI of 4.70, a pH optimum of 6.5, and was stable within a pH range of 5.5-7.5 and at temperatures below 55°C. It hydrolyzed p-nitrophenyl-β-D-xylopyranoside with a Km of 0.25mM and showed no activity against other p-nitrophenylglycosides containing p-nitrophenyl-α-D-xylopyranoside. The hydrolysis product from xylobiose, xylotriose, and xylotetraose was xylose. Xylopentaose was cleaved to xylose and a small amount of xylotetraose. Bacillus sp. XY-131 produced β-1, 4-xylanase besides β-xylosidase. These two enzymes were completely separated by DEAE-Toyopearl 650M column chromatography.
