PURIFICATION AND BIOCHEMICAL-CHARACTERIZATION OF BETA-XYLOSIDASE FROMHUMICOLA-GRISEA VAR THERMOIDEA

beta-D-Xylosidase production was maximal for Humicola grisea var. ther moidea grown on xylan as the sole carbon source. The main beta-D-xylos idase activity was localised in the periplasm. beta-Xylosidase was pur ified from crude extracts by heat treatment, ammonium sulfate precipit ation and chromatography on DEAE-cellulose and Sephadex G-100. The pur ified enzyme was a monomer of molecular mass estimated to be 43 kDa by SDS-PAGE and gel filtration. Optima of pH and temperature were 6.0 an d 50 degrees C, respectively. The enzyme activity was stimulated by Ca 2+, Fe2+, and Mg2+. The purified beta-xylosidase did not exhibit xylan ase, carboxymethylcelullase, galactosidase, glucosidase, fucosidase or arabinosidase activities. The purified beta-xylosidase hydrolysed xyl obiose and xylo-oligosaccharides of up to five monosaccharide units. T he enzyme had a K-m of 0.49 mM for p-nitrophenyl-beta-D-xylopyranoside and was not inhibited by its product, xylose.