Cloning, heterologous expression, and sequencing of a novel proline iminopeptidase gene, pepl. from Lactobacillus delbrueckii subsp. lactis DSM 7290

Fachbereich Biologie, Abteilung Mikrobiologie, Universität Kaiserslautern, Postfach 3049, 67653 Kaiserlautern, Germany Author for correspondence: Jürgen R. Klein. Tel: +49 631 205 2179. Fax: +49 631 205 2998 ABSTRACT The gene for proline iminopeptidase from Lactobacillus delbrueckii subsp. lactis DSM 7290 coding for an enzyme that hydrolyses the synthetic substrate L -prolyl-β-naphthylamide (Pro-βNA) was cloned in Escherichia coli . An enzymic plate assay was used to screen for positive clones. The gene, designated pepl, was subcloned into vector pUC18 and sequenced. The nucleotide sequence revealed an 882 bp open reading frame encoding 294 amino acids, coding for an enzyme with a calculated molecular mass of 32883 Da. By cloning under control of the lac promoter the peptidase was highly expressed. Sequence analysis showed that pepl is of a new sequence type, distinct from all peptidases so far sequenced. Amino acid homology to the active site of a Pseudomonas putida esterase and inhibitor studies of the enzyme imply involvement of a serine residue in catalysis. Keywords: iminopeptidase, serine protease, Lactobacillus delbrueckii subsp. lactis , nucleotide sequence analysis The GenBank/EMBL/DDBJ accession numbers for the novel nucleotide sequence data reported in this paper are Z26948 and Z26951 .