Molecular cloning and characterization of a M17 leucine aminopeptidase of Cryptosporidium parvum

Abstract

Leucine aminopeptidases (LAPs) are a group of metalloexopeptidases that catalyse the sequential removal of amino acids from the N-termini of polypeptides or proteins. They play an important role in regulating the balance between catabolism and anabolism in living cells. LAPs of apicomplexa parasitic protozoa have been intensively investigated due to their crucial roles in parasite biology as well as their potentials as drug targets. In this study, we identified an M17 leucine aminopeptidase of Cryptosporidium parvum (CpLAP) and characterized the biochemical properties of the recombinant protein. Multiple sequence alignment of the deduced amino acid sequence of CpLAP with those of other organisms revealed that typical amino acid residues essential for metal binding and active-site formation in M17 LAPs were well conserved in CpLAP. Recombinant CpLAP shared similar biochemical properties such as optimal pH, stability at neutral pHs, and metal-binding characteristics with other characterized LAPs. The enzyme showed a marked preference for Leu and its activity was effectively inhibited by bestatin. These results collectively suggest that CpLAP is a typical member of the M17 LAP family and may play an important role in free amino acid regulation in the parasite.