Hydrated electron-induced inactivation of tyrosinase in aqueous solution by exposure to cobalt-60 gamma-rays. II. Catecholase activity

Hiroaki Terato, O. Yamamoto

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Abstract

Tyrosinase (0.2 mg/ml) was irradiated with 60Co gamma-rays. The catecholase activity was measured at varying radiation doses under various atmospheric conditions. Do was found to be 1.25 kGy and hit number to be 2 in N2-saturated solution. OH radical scavengers t@?-BuOH and MeOH, had no effect. O2 which is an enhancer of OH-induced enzyme inactivation had little effect. But N2O as a e(aq) scavenger and Cu++ markedly protected against the inactivation indicating that e(aq) was the main species to inactivate the enzymatic activity. By Ultrogel chromatography, it was found that the enzymatic activity was lost when this enzyme dissociated into its subunits. Thus, it was concluded that the radiation-induced inactivation was due to the reduction of Cu++ as the active center and the chelater with e(aq) followed by the dissociation.

Original languageEnglish
Pages (from-to)301-307
Number of pages7
JournalBiochemistry and Molecular Biology International
Volume34
Issue number2
Publication statusPublished - Jan 1 1994
Externally publishedYes

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Monophenol Monooxygenase
Gamma Rays
Cobalt
Gamma rays
Electrons
Radiation
Enzymes
Chromatography
Dosimetry
hydroxide ion

ASJC Scopus subject areas

  • Biochemistry
  • Genetics
  • Molecular Biology

Cite this

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title = "Hydrated electron-induced inactivation of tyrosinase in aqueous solution by exposure to cobalt-60 gamma-rays. II. Catecholase activity",
abstract = "Tyrosinase (0.2 mg/ml) was irradiated with 60Co gamma-rays. The catecholase activity was measured at varying radiation doses under various atmospheric conditions. Do was found to be 1.25 kGy and hit number to be 2 in N2-saturated solution. OH radical scavengers t@?-BuOH and MeOH, had no effect. O2 which is an enhancer of OH-induced enzyme inactivation had little effect. But N2O as a e(aq) scavenger and Cu++ markedly protected against the inactivation indicating that e(aq) was the main species to inactivate the enzymatic activity. By Ultrogel chromatography, it was found that the enzymatic activity was lost when this enzyme dissociated into its subunits. Thus, it was concluded that the radiation-induced inactivation was due to the reduction of Cu++ as the active center and the chelater with e(aq) followed by the dissociation.",
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N2 - Tyrosinase (0.2 mg/ml) was irradiated with 60Co gamma-rays. The catecholase activity was measured at varying radiation doses under various atmospheric conditions. Do was found to be 1.25 kGy and hit number to be 2 in N2-saturated solution. OH radical scavengers t@?-BuOH and MeOH, had no effect. O2 which is an enhancer of OH-induced enzyme inactivation had little effect. But N2O as a e(aq) scavenger and Cu++ markedly protected against the inactivation indicating that e(aq) was the main species to inactivate the enzymatic activity. By Ultrogel chromatography, it was found that the enzymatic activity was lost when this enzyme dissociated into its subunits. Thus, it was concluded that the radiation-induced inactivation was due to the reduction of Cu++ as the active center and the chelater with e(aq) followed by the dissociation.

AB - Tyrosinase (0.2 mg/ml) was irradiated with 60Co gamma-rays. The catecholase activity was measured at varying radiation doses under various atmospheric conditions. Do was found to be 1.25 kGy and hit number to be 2 in N2-saturated solution. OH radical scavengers t@?-BuOH and MeOH, had no effect. O2 which is an enhancer of OH-induced enzyme inactivation had little effect. But N2O as a e(aq) scavenger and Cu++ markedly protected against the inactivation indicating that e(aq) was the main species to inactivate the enzymatic activity. By Ultrogel chromatography, it was found that the enzymatic activity was lost when this enzyme dissociated into its subunits. Thus, it was concluded that the radiation-induced inactivation was due to the reduction of Cu++ as the active center and the chelater with e(aq) followed by the dissociation.

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