Characterisation and preliminary X-ray diffraction analysis of human pancreatic procarboxypeptidase A2

Human procarboxypeptidase A2 has been expressed in a Pichia pastoris heterologous system and purified by hydrophobic interaction and anion exchange chromatographies. The hydrolytic action of carboxypeptidase A2 on peptide substrates with different lengths and residues at the C-terminus was analysed, and a preference towards long substrates with aromatic amino acids in their C-terminal end, particularly tryptophan, was found; with such substrates its activity is similar or higher than that of bovine carboxypeptidase A1. Procarboxypeptidase A2 has been crystallised using a vapour diffusion approach; the crystals obtained belong to the monoclinic system, spacegroup P21, and present one procarboxypeptidase A2 molecule per asymmetric unit. The crystals diffract beyond 1.8 Å resolution and are suitable for detailed X-ray analysis.