Prostaglandins production and some of their

Prostaglandins production and some of their possible biological functions have been reported in protozoa, helminths, and fungi organisms, for example amphizoic amoebas of the genus Acanthamoeba and Entamoeba (E. histolytica) produce PGA2, PGE2 and PGF2α [5,6]. PGA2 is believed to be an intrinsic osmoregulator in both parasites, whereas PGE2 is suspected of mediating pathogenicity of E. histolytica. This parasite stimulates hepatic production of PGE2, which induces inflammation and contributes to pathogenesis of amoebic abscesses [7]. It has also been shown that the PGE2 produced by E. histolytica alters the ionic permeability of the tight junctions in the colonic epithelium, inducing the appearance of diarrhea [8]. T. gondii tachyzoites produce PGE2, moreover, conditioned media of T. gondii-infected astrocytes has been reported to down modulate nitric oxide (NO) production by IFN-γ-activated microglia and recovery of neurite outgrowth. These effects were dependent on PGE2 production by the infected astrocytes and autocrine secretion of IL-10 by microglia [9]. Malaria infection is characterized by symptoms mediated by prostaglandins, which are thought to drive from host cells. However, the discovery of prostaglandin production in Plasmodium falciparum [10] does indicate the possibility of a substantial contribution of the parasite to malaria symptoms. Prostaglandin production has also been described in kinetoplastids. It has been reported that Trypanosoma brucei [11], T. cruzi [12], and Leishmania species [13] convert AA and PGH2 to prostaglandins by a pathway that is insensitive to the COX inhibitors indomethacin and aspirin. For example it has been reported that Leshmania donovani produces PGD2, PGE2, and PGF2α and the prostaglandin F2α synthase whereas in L. infantum chagasi the production of PGF2α synthase is carried out in the lipid bodies and its hiv protease inhibitor increases during the development of the parasite to a virulent metacyclic stage [14]. The existence of a prostaglandin F2α synthase in L. major and L. tropica has also been reported [13]. Even though some components of the route of production of prostaglandins in parasites are known, little or nothing is known about the enzymes that metabolize arachidonic acid (AA) in parasites. So far, only in E. histolytica, a COX-like enzyme has been described and isolated [15]; however it possess neither the arachidonate-binding domain, nor the heme-coordinating and catalytic sites, which are conserved in other species from higher organisms. COX like enzymes represent a missing link of prostaglandins production in parasites, and their relevance relays on the fact that their products modulate the immune system and most probably help parasites to produce these components to survive into their hosts. The aim of this work was to identify a protein responsible for COX activity in L. mexicana. As a first approach, we looked for antigenic and functional similarities to identify a COX-like enzyme; then, the protein with COX activity was purified by different chromatography procedures and its identity as gp63 was obtained by Mass Spectrometry. To further confirm that gp63 was the protein responsible for COX activity, a gp63 purification procedure was followed and COX activity was confirmed in those fractions containing enriched gp63. As an alternative but complementary approach we looked for conserved sequences and domains usually present in classical COX enzymes from higher eukaryotes, in parasite data bases. In this in silico analysis it was not possible to find any protein sequence with some degree of similarity to classical COX sequences; still, a structural alignment of COX sequences from Homo sapiens (COX-2) and Leishmania gp63 was analyzed to find the match between them. Finally, we demonstrate that a recombinant gp63 protein had COX-2 activity to finally identify to gp63 as the protein responsible for COX activity in L. mexicana.