Regulation of xylanolytic enzymes in Bacillus subtilis

The synthesis of the xylanolytic enzymes β-xylanase and β-xylosidase of Bacillus subtilis was studied. In contrast to many catabolic extracellular enzymes, β-xylanase was synthesized constitutively during exponential growth and was not repressed by glucose. β-Xylosidase synthesis was induced 100-fold by xylose and repressed 100-fold by glucose. Carbon catabolite repression was abolished in a ccpA mutant. Titration experiments using a multicopy operator sequence respondible for carbon catabolite repression indicated that the gene encoding β-xylosidase is part of the same carbon catabolite repression regulon as the amyE and bgIS genes.