Peptidase B (PEPB)

PepB encodes a 427-amino-acid protein, which can be unambiguously assigned to the leucyl aminopeptidase (LAP) structural family. PepB has been overexpressed and purified. The active enzyme shows many similarities to other members of the LAP family: it is a heat-stable hexameric metallopeptidase with a pH optimum of 8.5 to 9.5. A detailed study of the substrate specificity of the purified protein shows that it differs from other members of the family in its ability to hydrolyze peptides with N-terminal acidic residues. The preferred substrates for PepB are peptides with N-terminal Asp or Glu residues. Comparison of the amino acid sequence of PepB with those of other LAPs leads to the conclusion that PepB is the prototype of a new LAP subfamily with representatives in several other eubacterial species and to the prediction that the members of this family share the ability to hydrolyze peptides with N-terminal acidic residues.