This study reports the identification and characterization of a cAMP-specific phosphodiesterase from the parasitic hemoflagellateTrypanosoma brucei. TbPDE2A is a class I phosphodiesterase. Its catalytic domain exhibits 30–40% sequence identity with those of all 11 mammalian phosphodiesterase (PDE) families, as well as withPDE2fromSaccharomyces cerevisiae,duncefromDrosophila melanogaster, andregAfromDictyostelium discoideum. The overall structure of TbPDE2A resembles that of human PDE11A in that its N-terminal region contains a single GAF domain. This domain is very similar to those of the mammalian PDE2, -5, -6, -10, and -11, where it constitutes a potential cGMP binding site. TbPDE2A can be expressed inS. cerevisiae, and it complements anS. cerevisiaePDE deletion strain. Recombinant TbPDE2A is specific for cAMP, with aKmof ∼2 μm. It is entirely resistant to the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine, but it is sensitive to trequinsin, dipyridamole, sildenafil, and ethaverine with IC50values of 5.4, 5.9, 9.4, and 14.2 μm, respectively. All four compounds inhibit proliferation of bloodstream form trypanosomes in culture, indicating that TbPDE2A is an essential enzyme.
A reverse vaccinology approach to the identification and characterization of Ctenocephalides felis candidate protective antigens for the control of cat flea infestations
