SUMMARY: β-Glucanase synthesis in Bacillus subtilis was repressed by glucose and other substrates of glycolysis. Experiments with different pts mutants showed that the phosphoenolpyruvate:sugar phosphotransferase system is not involved in carbon catabolite repression of β-glucanase synthesis. Carbon catabolite repression of β-glucanase synthesis was completely abolished in a ccpA mutant. An operator structure similar to those upstream of amyE and the xyl operon was found and was shown by site-directed mutagenesis to be the target for carbon catabolite repression of β-glucanase synthesis. The presence of this operator on a multi-copy plasmid resulted in a reduced repression of both β-glucanase and α-amylase synthesis. It seems likely that the gene encoding these enzymes are part of one regulon with respect to catabolite repression.