Lysyl aminopeptidase (bacteria)

Publisher Summary This chapter describes the structural chemistry and the biological aspects of bacterial lysyl aminopeptidase. The bacterial lysyl aminopeptidase is a broad-specificity metallo-aminopeptidase. Peptidase N (PepN) is the most commonly used name for the enzyme belonging to family M1, which includes bacterial, fungal and mammalian enzymes. Generally, PepN is capable of hydrolyzing a broad range of peptides, removing the N-terminal amino acid. The lactococcal gene was designated pepN because it complemented an E. coli pepN mutation. PepN of Lactococcus lactis is active on di- and tripeptides, and on oligopeptides. Activity is optimal at 40°C. Most of the lysyl aminopeptidases are monomeric proteins of 95–97 kDa. They are identified as the members of the M1 peptidase family by the presence of an N-terminal conserved domain (pfam01433) of 393 amino acids. Among lactic acid bacteria, the amino acid sequences of PepN representatives are well conserved throughout their entire lengths of about 845 residues. No specific substrate is known that permits distinction from other general aminopeptidases. Cleavage studies with purified enzymes and transport studies indicate that the general aminopeptidases of Lactococcus—PepN, aminopeptidase C and peptidase T have overlapping but not identical specificities.