Hydrated electron-induced inactivation of tyrosinase in aqueous solution by exposure to cobalt-60 gamma-rays. I. Cresolase activity.
Tyrosinase (0.2 mg/ml of 0.1 M phosphate buffer solution, pH 6.5) which has cresolase and catecholase activities was irradiated with 60Co gamma-rays. The cresolase activity was measured at varying radiation doses under various atmospheric conditions. D0 was found to be 350 Gy in N2-saturated solution. The OH radical has been shown to be the main species involved in radiation-induced enzyme inactivation. However, in this study, OH radical scavengers, t-BuOH and MeOH, had no effect. O2 which acts generally as an enhancer of OH-induced enzyme inactivation also had little effect, but N20 ae aq scavenger, and Cu++ markedly inhibited the inactivation indicating that e aq is the main species involved in inactivating the cresolase activity, reducing Cu++ as the active center.
Division of Gene Chemistry, Graduate School of Gene Science, Faculty of Sciences, Hiroshima University, Japan.
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D001487:Basidiomycota / Q000201:enzymology; D002021:Buffers; D003037:Cobalt Radioisotopes; D003300:Copper / Q000494:pharmacology; D019327:Copper Sulfate; D004307:Dose-Response Relationship, Radiation; D016166:Free Radical Scavengers / Q000494:pharmacology; D005720:Gamma Rays; D017665:Hydroxyl Radical; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors / Q000528:radiation effects*; D010545:Peroxides / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000494:pharmacology; D012996:Solutions; D014867:Water; D020122:tert-Butylhydroperoxide
D002021:Buffers; D003037:Cobalt Radioisotopes; D016166:Free Radical Scavengers; D010545:Peroxides; D017382:Reactive Oxygen Species; D012996:Solutions; D014867:Water; D017665:Hydroxyl Radical; D003300:Copper; D020122:tert-Butylhydroperoxide; C028419:cuprous chloride; D014442:Monophenol Monooxygenase; D019327:Copper Sulfate