RESUMO
Inhibitors of PDE5 are useful therapeutic agents for treatment of erectile dysfunction. A series of novel xanthine derivatives has been identified as potent inhibitors of PDE5, with good levels of selectivity against other PDE isoforms, including PDE6. Studies in the dog indicate excellent oral bioavailability for compound 21.
Assuntos
3',5'-GMP Cíclico Fosfodiesterases/antagonistas & inibidores , Xantinas/farmacologia , Animais , Disponibilidade Biológica , Bovinos , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5 , Cães , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/uso terapêutico , Disfunção Erétil/tratamento farmacológico , Humanos , Concentração Inibidora 50 , Masculino , Farmacocinética , Isoformas de Proteínas/efeitos dos fármacos , Relação Estrutura-Atividade , Xantinas/químicaRESUMO
Deubiquitinating enzymes (DUBs) catalyze the removal of attached ubiquitin molecules from amino groups of target proteins. The large family of DUBs plays an important role in the regulation of the intracellular homeostasis of different proteins and influences therefore key events such as cell division, apoptosis, etc. The DUB family members UCH-L3 and USP2 are believed to inhibit the degradation of various tumor-growth-promoting proteins by removing the trigger for degradation. Inhibitors of these enzymes should therefore lead to enhanced degradation of oncoproteins and may thus stop tumor growth. To develop an enzymatic assay for the search of UCH-L3 and USP2 inhibitors, C-terminally labeled ubiquitin substrates were enzymatically synthesized. We have used the ubiquitin-activating enzyme E1 and one of the ubiquitin-conjugating enzymes E2 to attach a fluorescent lysine derivative to the C terminus of ubiquitin. Since only the epsilon-NH(2) group of the lysine derivatives was free and reactive, the conjugates closely mimic the isopeptide bond between the ubiquitin and the lysine side chains of the targeted proteins. Various substrates were synthesized by this approach and characterized enzymatically with the two DUBs. The variant consisting of the fusion protein between the large N-terminal NusA tag and the ubiquitin which was modified with alpha-NH(2)-tetramethylrhodamin-lysine, was found to give the highest dynamic range in a fluorescence polarization readout. Therefore we have chosen this substrate for the development of a miniaturized, fluorescence-polarization-based high-throughput screening assay.