Reaction of synthetic cyclic peroxide, 4-ethoxy-1,4-dihydro-2,3-benzodioxin-1-ol, with ferricytochrome c in vitro

• Published in: Biochimica et biophysica acta Vol. 967; no. 2; pp. 267 - 274
• Main Authors: Konishi, Tetsuya, Matsugo, Seiichi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 17.11.1988; Elsevier; North-Holland
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chemical Phenomena; Chemistry; Cyclic peroxide; Cytochrome c degradation; Cytochrome c Group; Dioxanes; Dioxins; Free Radicals; Fundamental and applied biological sciences. Psychology; Hemoproteins; Hydrogen-Ion Concentration; Hydroxyl radical; Metalloproteins; Oxidation-Reduction; Peroxide decomposition; Proteins; Time Factors; Cyclic peroxide; Peroxide decomposition; Cytochrome c degradation; Hydroxyl radical; Cytochrome c; Degradation; Temperature; Spectral properties; PH; Activation; Peroxides
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/0304-4165(88)90019-0

When synthetic cyclic peroxide, 4-ethoxy-1,4-dihydro-2,3-benzodioxin-1-ol (Bd), was added to a ferricytochrome c solution, the Soret band of cytochrome c at 410 nm gradually disappeared due to heme degradation. The reaction was prominent at pH < 7.5. At alkaline pH the reaction was markedly suppressed, despite the fact that decomposition of Bd itself occurred more rapidly at alkaline than acidic pH. Ferricytochrome c heme degradation occurred under anaerobic as well as aerobic conditions. On the other hand, ferrocytochrome c reacted directly with Bd and was oxidized, probably through the electron transfer mechanism. These results, together with the effect of deuterium isotope on the reaction, indicate that the heme degradation is mediated by the short-lived oxidative species generated directly from Bd decomposition. At alkaline pH, heme reduction rather than degradation predominated. The reaction was quantitatively inhibited by superoxide dismutase. Thus it was expected that the reduction was mediated by O 2 ⪰ produced secondarily from O 2 in the medium. The Bd-mediated cytochrome c degradation was weakly inhibited by dimethyl sulfoxide but was inhibited upto approximately 80% by mannitol or thiourea. Non-specific radical scavengers such as ascorbate inhibited the reaction almost completely.