Relationship between carbon catabolite repression and the biosynthesis regulation of the prolidase PepQ from Lactobacillus delbrueckii ssp. bulgaricus CNRZ 397

Lactobacillus delbrueckiissp. bulgaricus CNRZ 397 (L. bulgaricus) displays several enzymes specific of proline-containing peptides. We focused on the prolidase PepQ which specifi- cally cleaves X-Pro dipeptides. PepQ biosynthesis was previously shown to be independent of the pep- tide concentration of the culture medium in contrast to the cell surface proteinase PrtB and several aminopeptidases. Regulation of PepQ biosynthesis can be explained by the genetic organization of the region pepR1-cre-pepQ. The pepR1 gene encodes a CcpA-like regulator and its promoter harbors a cre site located immediately upstream of pepQ. Expression of fusions cre-pepQ-lacZand pepQ-lacZ in Bacillus subtilis showed that, under glucose conditions, the regulator CcpA acts as a transcriptional activator of pepQ expression. Analysis of PepQ biosynthesis in L. bulgaricus cells grown in differ- ent media is in agreement with a regulation dependent on carbohydrates. Lactobacillus delbrueckii ssp. bulgaricus / catabolite repression / PepQ / PepR1