title: Design and kinetic characterization of multisubstrate inhibitors of dopamine beta-hydroxylase.
abstract: The synthesis and kinetics characterization of a new class of dopamine beta-hydroxylase (DBH; EC 1.14.17.1) inhibitor, 1-(4-hydroxybenzyl)imidazole-2-thiol, is reported. These inhibitors, which incorporate a phenethylamine substrate mimic and an oxygen mimic into a single molecule, exhibit both the kinetic properties and the potency (Kis approximately 10(-9) M) expected for a multisubstrate inhibitor and are therefore classified as such. Steady-state kinetic experiments with these multisubstrate inhibitors and their substructural analogues support the recently proposed pH-dependent changes in substrate binding order [Ahn, N., & Klinman, J. P. (1983) Biochemistry 22, 3106] and a mechanism whereby the inhibitor binds specifically to the reduced Cu+ form of enzyme at both the phenethylamine substrate site and the active-site copper atom(s). A Yonetani-Theorell double-inhibition experiments indicates mutually exclusive binding of the inhibitor substructures p-cresol and 1-methylimidazole-2-thiol to suggest an extremely short intersite distance between the phenethylamine binding site and the active-site copper atom(s).
mesh_terms: D000818:Animals; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology; D004299:Dopamine beta-Hydroxylase / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000138:chemical synthesis* / Q000494:pharmacology; D007202:Indicators and Reagents; D007679:Kidney Medulla / Q000201:enzymology*; D007700:Kinetics; D008433:Mathematics; D013329:Structure-Activity Relationship
chemical_list: D007093:Imidazoles; D007202:Indicators and Reagents; C050962:1-(4-hydroxybenzyl)imidazole-2-thiol; D004299:Dopamine beta-Hydroxylase