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

β-Aminopeptidases are a unique group of enzymes that have the unusual capability to hydrolyze N-terminal β-amino acids from synthetic β-peptides. β-Peptides can form secondary structures mimicking α-peptide-like structures that are resistant to degradation by most known proteases and peptidases. These characteristics of β-peptides give them great potential as peptidomimetics. Here, the X-ray crystal structure of BcA5-BapA, a β-aminopeptidase from a Gram-negative 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 Å and showed a tetrameric assembly typical of the β-aminopeptidases. Each monomer consists of an α-subunit (residues 1-238) and a β-subunit (residues 239-367). Comparison of the structure of BcA5-BapA with those of other known β-aminopeptidases shows a highly conserved structure and suggests a similar proteolytic mechanism of action.β-Aminopeptidases are enzymes with the unique ability to hydrolyze N-terminal β-amino acids from synthetic β-peptides. Here, the crystal structure of a β-aminopeptidase isolated from a Burkholderia sp., BcA5-BapA, is reported. The BcA5-BapA structure shows a tetrameric arrangement, with each monomer adopting a four-layered αββα fold. Comparison with three characterized β-aminopeptidases shows that variation in the substrate-binding pockets may provide the basis for substrate specificity.