Exploration of the Binding Site of Arachidonic Acid in gp63 of Leishmania mexicana and in Orthologous Proteins in Clinically Important Parasites

Recently, we published that the monoclonal antibody (D12 mAb) recognizes gp63 of <i>L. mexicana</i>, and it is responsible for COX activity. This D12 mAb exhibited cross-reactivity with <i>Trypanosoma cruzi</i>, <i>Entamoeba histolytica</i>, <i>Acanthamoeba castellanii</i>, and <i>Naegleria fowleri</i>. COX activity assays performed in these parasites suggested the potential presence of such enzymatic activity. In our investigation, we confirmed that wild-type recombinant gp63 exhibits COX-like activity, in contrast to a mutated recombinant gp63 variant. Consequently, our objective was to identify sequences orthologous to gp63 and subsequently analyze the binding of arachidonic acid (AA) to the putative active sites of these proteins. Given the absence of a crystallized structure for this protein in the Protein Data Bank (PDB), it was imperative to first obtain a three-dimensional structure by homology modeling, using leishmanolysin from <i>Leishmania major</i> (PDB ID: LML1) as a template in the Swiss model database. The results obtained through molecular docking simulations revealed the primary interactions of AA close to the Zinc atom present in the catalytic site of gp63-like molecules of several parasites, predominantly mediated by hydrogen bonds with HIS264, HIS268 and HIS334. Furthermore, COX activity was evaluated in commensal species such as <i>E. dispar</i> and during the encystment process of <i>E. invadens</i>.