Crystal structure of a β-aminopeptidase from an Australian Burkholderia sp.

beta-Aminopeptidases are a unique group of enzymes that have the unusual capability to hydrolyze N-terminal beta-amino acids from synthetic beta-peptides. beta-Peptides can form secondary structures mimicking beta-peptide-like structures that are resistant to degradation by most known proteases and peptidases. These characteristics of beta-peptides give them great potential as peptidomimetics. Here, the X-ray crystal structure of BcA5-BapA, a beta-aminopeptidase from a Gramnegative Burkholderia sp. that was isolated from activated sludge from a wastewater-treatment plant in Australia, is reported. The crystal structure of BcA5-BapA was determined to a resolution of 2.0 angstrom and showed a tetrameric assembly typical of the beta-aminopeptidases. Each monomer consists of an beta-subunit (residues 1-238) and a beta-subunit (residues 239-367). Comparison of the structure of BcA5-BapA with those of other known beta-aminopeptidases shows a highly conserved structure and suggests a similar proteolytic mechanism of action.