<i>PFPI</i>-like genes are expressed in <i>Leishmania major</i> but are pseudogenes in other <i>Leishmania</i> species

&lt;i&gt;Pyrococcus furiosus&lt;/i&gt; protease I (PFPI) is a multimeric cysteine peptidase from &lt;i&gt;P. furiosus&lt;/i&gt;. Genome analyses indicate that orthologues are present in rather few other organisms, including &lt;i&gt;Dictyostelium discoideum&lt;/i&gt; and several bacteria, Archaea and plants. An open reading frame (ORF) coding for a PFPI-like protein (PFP1) was identified in &lt;i&gt;Leishmania&lt;/i&gt; major and &lt;i&gt;Leishmania mexican&lt;/i&gt; and full-length spliced and polyadenylated &lt;i&gt;PFP1&lt;/i&gt; mRNA detected for both species. Vestiges of a PFPI-like gene could also be identified in &lt;i&gt;Leishmania braziliensis&lt;/i&gt; and &lt;i&gt;Leishmania infantum&lt;/i&gt;, but no ORF remains owing to the presence of frame-shifts and stop codons. No evidence for a &lt;i&gt;PFPI&lt;/i&gt;-like gene could be found in the syntenic region of &lt;i&gt;Trypanosoma brucei&lt;/i&gt; or &lt;i&gt;Trypanosoma cruzi&lt;/i&gt;, raising the possibility that the &lt;i&gt;PFPI&lt;/i&gt;-like genes were acquired by a lateral gene transfer event after the divergence of trypanosomes and &lt;i&gt;Leishmania&lt;/i&gt;. The gene may have subsequently degenerated into a pseudogene in some &lt;i&gt;Leishmania&lt;/i&gt; species, owing to the loss of relevant biological function. However, antibodies raised against &lt;i&gt;L. mexicana&lt;/i&gt; recombinant protein detected PFP1 in promastigote extracts of &lt;i&gt;L. major&lt;/i&gt;, but not in &lt;i&gt;L. Mexicana&lt;/i&gt; promastigote or amastigote extracts. The expression of &lt;i&gt;PFP1&lt;/i&gt; in &lt;i&gt;L. major&lt;/i&gt; suggests that PFP1 might contribute to the disease tropism that distinguishes this &lt;i&gt;Leishmania&lt;/i&gt; species from others