title: Biological and structural characterization of Trypanosoma cruzi phosphodiesterase C and Implications for design of parasite selective inhibitors.
abstract: Trypanosoma cruzi phosphodiesterase C (TcrPDEC) is a potential new drug target for the treatment of Chagas disease but has not been well studied. This study reports the enzymatic properties of various kinetoplastid PDECs and the crystal structures of the unliganded TcrPDEC1 catalytic domain and its complex with an inhibitor. Mutations of PDEC during the course of evolution led to inactivation of PDEC in Trypanosoma brucei/Trypanosoma evansi/Trypanosoma congolense, whereas the enzyme is active in all other kinetoplastids. The TcrPDEC1 catalytic domain hydrolyzes both cAMP and cGMP with a K(m) of 23.8 μm and a k(cat) of 31 s(-1) for cAMP and a K(m) of 99.1 μm and a k(cat) of 17 s(-1) for cGMP, thus confirming its dual specificity. The crystal structures show that the N-terminal fragment wraps around the TcrPDEC catalytic domain and may thus regulate its enzymatic activity via direct interactions with the active site residues. A PDE5 selective inhibitor that has an IC(50) of 230 nm for TcrPDEC1 binds to TcrPDEC1 in an orientation opposite to that of sildenafil. This observation, together with the screen of the inhibitory potency of human PDE inhibitors against TcrPDEC, implies that the scaffold of some human PDE inhibitors might be used as the starting model for design of parasite PDE inhibitors. The structural study also identified a unique parasite pocket that neighbors the active site and may thus be valuable for the design of parasite-specific inhibitors.
authors.affiliation: Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA
authors.forename: Huanchen
authors.initials: H
authors.lastname: Wang
authors.forename: Stefan
authors.initials: S
authors.lastname: Kunz
authors.forename: Gong
authors.initials: G
authors.lastname: Chen
authors.forename: Thomas
authors.initials: T
authors.lastname: Seebeck
authors.forename: Yiqian
authors.initials: Y
authors.lastname: Wan
authors.forename: Howard
authors.initials: H
authors.lastname: Robinson
authors.forename: Sibylla
authors.initials: S
authors.lastname: Martinelli
authors.forename: Hengming
authors.initials: H
authors.lastname: Ke
mesh_terms: D000595:Amino Acid Sequence; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D015195:Drug Design; D007700:Kinetics; D008969:Molecular Sequence Data; D010726:Phosphodiesterase Inhibitors / Q000737:chemistry*; D010727:Phosphoric Diester Hydrolases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D013449:Sulfonamides / Q000737:chemistry*; D013499:Surface Properties; D014349:Trypanosoma cruzi / Q000201:enzymology*
chemical_list: C572496:5-(2-ethoxy-5-(N-isopropyloxycarbonyl-aminosulfonyl))-1-methyl-3-propyl-1H-pyrazolo(4,3-d)pyrimidin-7(6H)-one; D019086:Bridged Bicyclo Compounds, Heterocyclic; D010726:Phosphodiesterase Inhibitors; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D013449:Sulfonamides; D010727:Phosphoric Diester Hydrolases