Characterization of TbPDE2A, a Novel Cyclic Nucleotide-specific Phosphodiesterase from the Protozoan Parasite Trypanosoma brucei

This study reports the identification and characterization of a cAMP-specific phosphodiesterase from the parasitic hemoflagellate Trypanosoma 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 with PDE2fromSaccharomyces cerevisiae, dunce fromDrosophila melanogaster, and regA fromDictyostelium 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 in S. cerevisiae, and it complements an S. cerevisiae PDE deletion strain. Recombinant TbPDE2A is specific for cAMP, with aKm of ∼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 IC50 values 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.