Characterization of the Lactococcus lactis pepN gene encoding an aminopeptidase homologous to mammalian aminopeptidase N

The nucleotide sequence of the pepN gene from Lactococcus lactis encoding a zinc-metallo aminopeptidase has been determined. The open reading frame of 2,538 base pairs encodes a protein with a calculated M(r) of 95,368, which agrees with the apparent M(r) of 95,000 of the gene product which was identified by polyclonal antibodies raised against the purified aminopeptidase. The amino acid sequence of the aminopeptidase of L. lactis was found to be similar to the corresponding enzymes of human, rat and mouse, with almost 30% of the residues identical. Also, a highly conserved area was identified which has similarity with the active site of thermolysin. A zinc-binding site, as well as the catalytic site for PepN, is predicted to lie within this conserved stretch. Putative promoter regions upstream of PepN were confirmed by primer extension analysis

Synthetic Mimic of Antimicrobial Peptide with Nonmembrane-Disrupting Antibacterial Properties

Proteolysis in dairy lactic acid bacteria has been studied in great detail by genetic, biochemical and ultrastructural methods. From these studies the picture emerges that the proteolytic systems of lactococci and lactobacilli are remarkably similar in their components and mode of action. The proteolytic system consists of an extracellularly located serine-proteinase, transport systems specific for di-tripeptides and oligopeptides (> 3 residues), and a multitude of intracellular peptidases. This review describes the properties and regulation of individual components as well as studies that have led to identification of their cellular localization. Targeted mutational techniques developed in recent years have made it possible to investigate the role of individual and combinations of enzymes in vivo. Based on these results as well as in vitro studies of the enzymes and transporters, a model for the proteolytic pathway is proposed. The main features are: (i) proteinases have a broad specificity and are capable of releasing a large number of different oligopeptides, of which a large fraction falls in the range of 4 to 8 amino acid residues; (ii) oligopeptide transport is the main route for nitrogen entry into the cell; (iii) all peptidases are located intracellularly and concerted action of peptidases is required for complete degradation of accumulated peptides.

THE BIOCHEMICAL, GENETIC AND PHYSIOLOGICAL-PROPERTIES OF AMINOPEPTIDASE-N FROM LACTOCOCCUS-LACTIS

In the flavor development peptidases play a very important role since the wide variety of peptides and amino acids released by these enzymes determine to a large extent the flavors and off-flavors (bittertaste) in cheese. Therefore, knowledge about the activity and substrate specificity of the peptidases will contribute to a better understanding of the complex process of cheese ripening. This thesis describes the investigations of an aminopeptidase in lactococctus lactis. ... Zie: Summar