PURIFICATION AND REGULATION OF THE SYNTHESIS OF A BETA-XYLOSIDASE FROM ASPERGILLUS-NIDULANS

beta-Xylosidase (EC 3.2.1.37) has been purified from Aspergillus nidul ans mycelium grown on oat-spelt xylan as sole carbon source. Its pH op timum for activity was found to be 5.0 and the optimum temperature was 50 degrees C. Its molecular mass was estimated by gel filtration to b e 180 000. Using p-nitrophenyl-beta-D-xylopyranoside as substrate, the K-m and V-max values have been found to be 1.1 mM and 25.6 mu mol min (-1) (mg protein)(-1), respectively. Enzyme activity was inhibited by Hg2+ Ag2+, and Cu2+ at a concentration of 1 x 10(-3) M. The synthesis of beta-xylosidase in A. nidulans is strongly induced by; arabinose an d xylose and is subject to carbon catabolite repression mediated by th e creA gene product.