Regulation of xylanolytic enzymes in Bacillus subtilis

The synthesis of the xylanolytic enzymes beta-xylanase and beta-xylosidase of Bacillus subtilis was studied. In contrast to many catabolic extracellular enzymes, beta-xylanase was synthesized constitutively during exponential growth and was not repressed by glucose. beta-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 responsible for carbon catabolite repression indicated that the gene encoding beta-xylosidase is part of the same carbon catabolite repression regulon as the amyE and bgIS genes.