CLONING, SEQUENCING AND CHARACTERIZATION OF THE PEPIP GENE ENCODING APROLINE IMINOPEPTIDASE FROM LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS CNRZ-397

The proline iminopeptidase (PepIP) of Lactobacillus delbrueckii subsp. bulgaricus is a major peptidase located in the cell envelope. Its str uctural gene (pepIP) has been cloned into pUC18 and expressed at a ver y high level in Escherichia coli to give a PepIP activity 15 000-fold higher than that found in L. delbrueckii subsp. bulgaricus. The nucleo tide sequence of the pepIP gene revealed an open reading frame of 295 codons encoding a protein with a predicted M(r) of 33 006, which is co nsistent with the apparent size of the gene product. The amino acid se quence of PepIP shows significant homology with those of other hydrola ses involved in the degradation of cyclic compounds. In particular, th ere is a region which includes an identified catalytic site containing a serine residue and a motif specific for the active sites of prolylo ligopeptidases (Gly-X-Ser-X-Gly-Gly). The PepIP opens a new way for su pplying cells with proline using the peptides resulting from the prote olytic degradation of caseins.