Dopamine beta-hydroxylase inactivation generates a protein-bound quinone derivative.
Bovine dopamine beta-hydroxylase (DbH) was inactivated by hydrogen peroxide and ascorbate in the presence of dioxygen. Both inactivated forms of the enzyme were investigated. We could highlight the presence of a quinone derivative bound to the protein, assumed as being dopa-quinone, that is absent from active enzyme. Such results suggest that a tyrosinyl radical transiently forms during catalysis. Moreover we could show that addition of substrate tyramine to H2O2 incubates is responsible for a partial protection of DbH against inactivation.
Chimie, Biologie et Radicaux libres, UMR-CNRS 6517, Faculté des Sciences et Techniques de St-Jérome, case 432, Av. Escadrille Normandie-Niémen, 13397 Cedex 20, Marseille, France.
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D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D002417:Cattle; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000737:chemistry*; D004299:Dopamine beta-Hydroxylase / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D006861:Hydrogen Peroxide / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014439:Tyramine / Q000737:chemistry; D014466:Ultraviolet Rays
D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D006861:Hydrogen Peroxide; D004299:Dopamine beta-Hydroxylase; D001205:Ascorbic Acid; D010100:Oxygen; D014439:Tyramine