Reduction of ubiquinone-1 by ascorbic acid is a catalytic and reversible process controlled by the concentration of molecular oxygen

被引:14
作者
Roginsky, VA
Mohr, D
Stocker, R
机构
[1] Biochemistry Group, Heart Research Institute, Camperdown, Sydney
关键词
D O I
10.1080/13510002.1996.11747027
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
To address whether reduction by vitamin C may contribute to the in vivo maintenance of coenzyme Q in the reduced form, we studied the reduction of ubiquinone-1 by ascorbate at pH 7.4, Addition of ascorbate to ubiquinone-l resulted in rapid O-2 consumption and an increase in the steady-state concentration of ascorbyl radical, The initial rate of O-2 consumption was proportional to the product of [ubiquinone-1] and [ascorbate] whereas [ascorbyl radical] was proportional to the square root of this parameter; both dependencies were in quantitative agreement with each other, The extent of O-2 consumption greatly exceeded the amounts of ubiquinone-l initially present, Formation of ubiquinol-l from ubiquinone-l by ascorbate was reversible, moderate under aerobic conditions, but substantial in the absence or near absence of oxygen, At high O-2 concentration, ascorbate promoted the oxidation of ubiquinol-l to ubiquinone-l, Addition of sodium dodecyl sulphate dramatically decreased the rate of reaction between ubiquinone-l and ascorbate, most likely as a result of phase separation of the reagents, A. preliminary reaction scheme with putative rate constants for the relevant reactions is presented that quantitatively describes the kinetic behaviour of the process studied, The key reactions in the scheme are electron transfer from ascorbate to ubiquinone-l with formation of the ascorbyl and ubisemiquinone radical, The reaction of the latter with O-2 is postulated to be responsible for O-2 consumption, with ubiquinone-l acting as a catalyst, Together, the results demonstrate that the extent of reduction of ubiquinone-l by ascorbate was controlled by the O-2 concentration and the physical availability of the reactants, As the O-2 concentration in human blood is relatively high and ubiquinone-10 is located exclusively within the lipid phase of lipoproteins where negatively charged ascorbate has little access, our results suggest that direct reduction by ascorbate is unlikely to be responsible for the high reduction percentage observed for plasma coenzyme Q.
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页码:55 / 62
页数:8
相关论文
共 27 条
[1]   DISTRIBUTION AND REDOX STATE OF UBIQUINONES IN RAT AND HUMAN TISSUES [J].
ABERG, F ;
APPELKVIST, EL ;
DALLNER, G ;
ERNSTER, L .
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 1992, 295 (02) :230-234
[2]   THE PARTICIPATION OF COENZYME-Q IN FREE-RADICAL PRODUCTION AND ANTIOXIDATION [J].
BEYER, RE .
FREE RADICAL BIOLOGY AND MEDICINE, 1990, 8 (06) :545-565
[3]   TOCOPHEROL-MEDIATED PEROXIDATION - THE PROOXIDANT EFFECT OF VITAMIN-E ON THE RADICAL-INITIATED OXIDATION OF HUMAN LOW-DENSITY-LIPOPROTEIN [J].
BOWRY, VW ;
STOCKER, R .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1993, 115 (14) :6029-6044
[4]   ASCORBATE FREE-RADICAL AS A MARKER OF OXIDATIVE STRESS - AN EPR STUDY [J].
BUETTNER, GR ;
JURKIEWICZ, BA .
FREE RADICAL BIOLOGY AND MEDICINE, 1993, 14 (01) :49-55
[5]  
BURLAKOVA EB, 1985, USP KHIM+, V54, P1540
[6]   UBIQUINOL-3 AND UBIQUINOL-7 EXHIBIT SIMILAR ANTIOXIDANT ACTIVITY IN MODEL MEMBRANES [J].
FIORENTINI, D ;
CABRINI, L ;
LANDI, L .
FREE RADICAL RESEARCH COMMUNICATIONS, 1993, 18 (04) :201-209
[7]   INHIBITION OF LIPID-PEROXIDATION BY UBIQUINOL IN SUBMITOCHONDRIAL PARTICLES IN THE ABSENCE OF VITAMIN-E [J].
FORSMARK, P ;
ABERG, F ;
NORLING, B ;
NORDENBRAND, K ;
DALLNER, G ;
ERNSTER, L .
FEBS LETTERS, 1991, 285 (01) :39-43
[8]   UBIQUINOL-10 IS AN EFFECTIVE LIPID-SOLUBLE ANTIOXIDANT AT PHYSIOLOGICAL CONCENTRATIONS [J].
FREI, B ;
KIM, MC ;
AMES, BN .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 1990, 87 (12) :4879-4883
[9]   AUTOXIDATION OF LIPIDS AND ANTIOXIDATION BY ALPHA-TOCOPHEROL AND UBIQUINOL IN HOMOGENEOUS SOLUTION AND IN AQUEOUS DISPERSIONS OF LIPIDS - UNRECOGNIZED CONSEQUENCES OF LIPID PARTICLE-SIZE AS EXEMPLIFIED BY OXIDATION OF HUMAN LOW-DENSITY-LIPOPROTEIN [J].
INGOLD, KU ;
BOWRY, VW ;
STOCKER, R ;
WALLING, C .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 1993, 90 (01) :45-49
[10]   ANTIOXIDANT EFFECTS OF UBIQUINONES IN MICROSOMES AND MITOCHONDRIA ARE MEDIATED BY TOCOPHEROL RECYCLING [J].
KAGAN, V ;
SERBINOVA, E ;
PACKER, L .
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 1990, 169 (03) :851-857