A novel aminopeptidase from Burkholderia cepacia specific for acidic amino acids

An aminopeptidase specific for the N-terminal acidic residue (BcepAP) was purified from the cell extract of Burkholderia cepacia svr as a homotrimeric (subunit mass 66 kDa) molecule. It was identified as an unassigned peptidase of family M61. The only other member characterized so far from this family is a broad-specificity aminopeptidase of Sphingomonas capsulata (ScapAP) with preference for Gly or Ala residues. However, BcepAP exhibited narrow specificity and the preferred substrate was a peptide with an N-terminal Asp or Glu residue, which is quite unusual. The proteins assigned to this family were grouped separately on the basis of their homology to either BcepAP or ScapAP. It led the conclusion that BcepAP is a prototype of a new PepM61 subfamily, with a representative in other Proteobacteria, and to the prediction that members of the family share the ability to cleave N-terminal acidic residues of peptide substrates.