National Center for
3P8P: Crystal Structure of Human Dimethylarginine Dimethylaminohydrolase-1 (DDAH-1) variant C274S bound with N5-(1-iminopentyl)-L-ornithine
ChemMedChem (2011) 6 p.81-88
C-Alkyl amidine analogues of asymmetric N(omega),N(omega)-dimethyl-L-arginine are dual-targeted inhibitors of both human DDAH-1 and nitric oxide (NO) synthase, and provide a promising scaffold for the development of therapeutics to control NO overproduction in a variety of pathologies including septic shock and some cancers. Using a two-part click-chemistry-mediated activity probe, a homologated series of C-alkyl amidines were ranked for their ability to inhibit DDAH-1 within cultured HEK 293T cells. N(5)-(1-Iminopentyl)-L-ornithine was determined to be the most potent compound in vitro (K(d)=7 muM) as well as in cultured cells, and the binding conformation and covalent reversible mode of inhibition was investigated by comparison of interactions made with DDAH-1 and a catalytically inactive C274S variant, as gauged by X-ray crystallography and isothermal titration calorimetry. By interrupting the ability of the inhibitor to form a covalent bond, the contribution of this interaction could be estimated. These results suggest that further stabilization of the covalent adduct is a promising strategy for lead optimization in the design of effective reagents to block NO synthesis.