Mechanisms of sulfoxidation catalyzed by high-valent intermediates of heme enzymes: Electron-transfer vs oxygen-transfer mechanism

Yoshio Goto, Toshitaka Matsui, Shin Ichi Ozaki, Yoshihito Watanabe, Shunichi Fukuzumi

研究成果: Article査読

145 被引用数 (Scopus)

抄録

Mechanisms of sulfoxidation catalyzed by high-valent intermediates of heme enzymes have been investigated by direct observation of sulfide-induced reduction of three different compound I species including HRP (horseradish peroxidase), the His64Ser myoglobin (Mb) mutant, and O=Fe(IV)TMP+· (1) (TMP = 5,10,15,20-tetramesitylporphyrin dianion). The reaction of thioanisole and compound I of HRP (10 μM, pH 7.0, 298 K) gives the resting state of HRP with accumulation of compound II as an intermediate. The yield of sulfoxide by a stoichiometric reaction of HRP compound I with thioanisole was only 25% ± 5%. On the other hand, the same sulfoxidation by both 1 and His64Ser Mb compound I exclusively exhibited a two-electron process, resulting in quantitative formation of sulfoxide. When 1,5-dithiacyclooctane (DTCO) is employed as a substrate, the reaction of His64Ser Mb compound I with DTCO exhibits rapid formation of compound II, which decays to the ferric state due to the low oxidation potential of DTCO. The observed rate constants (log k(obs)) of the reactions of 1 and compounds I of HRP and His64Ser Mb with a series of p-substituted thioanisoles correlate with the one-electron oxidation potentials (E(ox)/0) of the sulfides. A comparison of these correlations with the established correlation between log k(obs) and E(ox)/0 for the corresponding electron-transfer reactions of substituted N,N- dimethylanilines has revealed that the sulfoxidation reactions of compound I of HRP with the sulfides proceed via electron transfer while the sulfoxidations catalyzed by 1 and compound I of His64Ser Mb occur via direct oxygen transfer.

本文言語English
ページ(範囲)9497-9502
ページ数6
ジャーナルJournal of the American Chemical Society
121
41
DOI
出版ステータスPublished - 1999 10 20
外部発表はい

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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