DT-diaphorase-catalyzed two-electron reduction of various p-benzoquinone- and 1,4-naphthoquinone epoxides

Journal Article · Fri Jan 01 04:00:00 EST 1988 · Free Radical Biology and Medicine; (USA)

DOI:https://doi.org/10.1016/0891-5849(88)90076-7· OSTI ID:5668484

Brunmark, A; Cadenas, E; Segura-Aguilar, J; Lind, C; Ernster, L ^[1]

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1. Univ. of Linkoeping (Sweden)

The oxidation of various quinones by H{sub 2}O{sub 2} results in quinone epoxide formation. The yield of epoxidation is inversely related to the degree of methyl substitution of the quinone and seems not to be dependent on the redox potential of the quinones studied. The following order of H{sub 2}O{sub 2}-mediated epoxidation of quinones was found: p-benzoquinone greater than or equal to 1,4-naphthoquinone greater than 2-methyl-p-benzoquinone greater than 2,6-dimethyl-p-benzoquinone greater than or equal to 2-methyl-1,4-naphthoquinone greater than 2,3-dimethyl-1,4-naphthoquinone. DT-Diaphorase reduces several quinone epoxides at different rates. The rate of quinone epoxide reduction cannot be related to either the redox potential of the quinone epoxide (as reflected by the half-wave potential calculated from the corresponding hydrodynamic voltamograms) or the degree of substitution of the quinone epoxide. It appears, however, that a quinone epoxide redox potential more negative than -0.5 to -0.6 volts settles a threshold for the electron transfer reaction. This does not exclude that specificity requirements, i.e. the formation of the quinone epoxide substrate-enzyme complex may chiefly determine the rate of reduction of quinone epoxides by DT-diaphorase. DT-diaphorase-catalyzed two-electron transfer to quinone epoxides--resulting in epoxide ring opening--yields 2-OH-p-benzohydroquinone or 2-OH-1,4-naphthohydroquinone products. These hydroxy-derivatives show a higher rate of autoxidation than do the parent hydroquinones lacking the OH substituent.

• OSTI ID: 5668484
• Journal Information: Free Radical Biology and Medicine; (USA), Journal Name: Free Radical Biology and Medicine; (USA) Vol. 5:3; ISSN FRBME; ISSN 0891-5849
• Country of Publication: United States
• Language: English

Related Subjects

560300* -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AROMATICS
BIOLOGICAL EFFECTS
CHEMICAL REACTIONS
ELECTRON TRANSFER
EPOXIDES
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
METABOLISM
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXYGEN COMPOUNDS
PEROXIDES
QUINONES
REDOX POTENTIAL
REDOX REACTIONS
SPECIFICITY