Purification and regulation of the synthesis of a β-xylosidase fromAspergillus nidulans

PXylosidase (EC 3.2.1.37)has been purified from Aspergillus nidulans mycelium grown on oat-spelt xylan as sole carbon source.Its pH optimum for activity was found to be 5.0 and the optimum temperature was 50°C.Its molecular mass was estimated by gel filtration to be 180000.Using p-nitrophenyl-P-D-xylopyranoside as substrate, the K, and V,,,,, values have been found to be 1 .lmM and 25.6 wrnol min-' (mg protein)-', respectivdy.Enzyme activity was inhibited by Hg'+, Ag2+, and CL?+ at a concentration of 1 X lop3 M. The synthesis of /3-xylosidase in A. nidulans is strongly induced by arabinose and xylose and is subject to carbon catabolite repression mediated by the creA gene product.