TY - JOUR
T1 - Nitration of γ-tocopherol and oxidation of α-tocopherol by copper-zinc superoxide dismutase/H2O2/NO2-
T2 - Role of nitrogen dioxide free radical
AU - Singh, Ravinder J.
AU - Goss, Steven P.A.
AU - Joseph, Joy
AU - Kalyanaraman, B.
PY - 1998/10/27
Y1 - 1998/10/27
N2 - Copper-zinc Superoxide dismutase (Cu,Zn-SOD) is the antioxidant enzyme that catalyzes the dismutation of Superoxide (O2.-) to O2 and H2O2. In addition, Cu,ZnSOD also exhibits peroxidase activity in the presence of H2O2, leading to self-inactivation and formation of a potent enzyme-bound oxidant. We report in this study that lipid peroxidation of L-α-lecithin liposomes was enhanced greatly during the SOD/H2O2 reaction in the presence of nitrite anion (NO2-) with or without the metal ion chelator, diethylenetriaminepentacetic acid. The presence of NO2- also greatly enhanced α-tocopherol (α-TH) oxidation by SOD/H2O2 in saturated 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine liposomes. The major product identified by HPLC and UV-studies was α-tocopheryl quinone. When 1,2-diauroyl-sn-glycero-3-phosphatidylcholine liposomes containing γ-tocopherol (γ-TH) were incubated with SOD/H2O2/NO2-, the major product identified was 5-NO2-γ-TH. Nitrone spin traps significantly inhibited the formation of α-tocopheryl quinone and 5-NO2-γ-TH. NO2- inhibited H2O2-dependent inactivation of SOD. A proposed mechanism of this protection involves the oxidation of NO2- by an SOD-bound oxidant to the nitrogen dioxide radical (.NO2). In this study, we have shown a new mechanism of nitration catalyzed by the peroxidase activity of SOD. We conclude that NO2- is a suitable probe for investigating the peroxidase activity of familial Amyotrophic Lateral Sclerosis-linked SOD mutants.
AB - Copper-zinc Superoxide dismutase (Cu,Zn-SOD) is the antioxidant enzyme that catalyzes the dismutation of Superoxide (O2.-) to O2 and H2O2. In addition, Cu,ZnSOD also exhibits peroxidase activity in the presence of H2O2, leading to self-inactivation and formation of a potent enzyme-bound oxidant. We report in this study that lipid peroxidation of L-α-lecithin liposomes was enhanced greatly during the SOD/H2O2 reaction in the presence of nitrite anion (NO2-) with or without the metal ion chelator, diethylenetriaminepentacetic acid. The presence of NO2- also greatly enhanced α-tocopherol (α-TH) oxidation by SOD/H2O2 in saturated 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine liposomes. The major product identified by HPLC and UV-studies was α-tocopheryl quinone. When 1,2-diauroyl-sn-glycero-3-phosphatidylcholine liposomes containing γ-tocopherol (γ-TH) were incubated with SOD/H2O2/NO2-, the major product identified was 5-NO2-γ-TH. Nitrone spin traps significantly inhibited the formation of α-tocopheryl quinone and 5-NO2-γ-TH. NO2- inhibited H2O2-dependent inactivation of SOD. A proposed mechanism of this protection involves the oxidation of NO2- by an SOD-bound oxidant to the nitrogen dioxide radical (.NO2). In this study, we have shown a new mechanism of nitration catalyzed by the peroxidase activity of SOD. We conclude that NO2- is a suitable probe for investigating the peroxidase activity of familial Amyotrophic Lateral Sclerosis-linked SOD mutants.
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U2 - 10.1073/pnas.95.22.12912
DO - 10.1073/pnas.95.22.12912
M3 - Article
C2 - 9789014
AN - SCOPUS:0032573172
SN - 0027-8424
VL - 95
SP - 12912
EP - 12917
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 22
ER -