title: Oxygen binding to tyrosinase from streptomyces antibioticus studied by laser flash photolysis.
abstract: Tyrosinases catalyze the o-hydroxylation of monophenols (monophenolase activity) and the oxidation of o-diphenols to o-quinones (diphenolase activity) and possess a dinuclear copper active site. The O2 binding kinetics of oxytyrosinase is studied by flash-photolysis measurements, and the O2 binding rate constant (kO2) is obtained as kO2 = 13 +/- 3 muM-1 s-1. Small molecules, such as carbon monoxide and p-nitrophenol (a substrate-analogue inhibitor), are demonstrated to affect O2 binding kinetics. The activation enthalpy of the rate-limiting step of O2 binding is calculated by the temperature dependence of kO2 to be 12.8 +/- 2.6 kcal/mol.
authors.affiliation: Department of Physical Chemistry, 21st Century COE Program, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. hirota@mb.kyoto-phu.ac.jp
authors.forename: Shun
authors.initials: S
authors.lastname: Hirota
authors.forename: Takumi
authors.initials: T
authors.lastname: Kawahara
authors.forename: Emanuela
authors.initials: E
authors.lastname: Lonardi
authors.forename: Ellen
authors.initials: E
authors.lastname: de Waal
authors.forename: Noriaki
authors.initials: N
authors.lastname: Funasaki
authors.forename: Gerard W
authors.initials: GW
authors.lastname: Canters
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D010782:Photolysis; D013303:Streptomyces antibioticus / Q000201:enzymology*; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D014442:Monophenol Monooxygenase; D010100:Oxygen