Table 1 |
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|
Equations |
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| Oxygen radical generation |
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| NADPH oxidase: |
2O2 + NADPH |
→ |
2O2•- (superoxide) + NADPH+ + H+ |
| Spontaneous conversion: |
2O2•- + 2H+ |
→ |
[2HO2• (hydroperoxyl radical)] → O2 + H2O2 |
| Superoxide dismutase: |
2O2•- + 2H+ |
→ |
O2 + H2O2 |
| Myeloperoxidase: |
Cl- + H2O2 |
→ |
OCl- (oxidised halide) + H2O |
| Reactive oxygen species secondary products |
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| H2O2 + Fe2+ |
→ |
OH- + OH• (hydroxyl radical) + Fe3+ |
|
| Fe3+ + O2•- |
→ |
O2 + Fe2+ |
|
| O2•- + HOCl |
→ |
O2•- + OH• + Cl- |
|
| H2O2 + OCl- |
→ |
1O2 (singlet oxygen) + H2O + Cl- |
|
| NH3 + HOCl |
→ |
NH2Cl (chloramine) + H2O |
|
| R-CHNH2-COOH + HOCl → |
R-CHNHCl-COOH + H2O → |
R-CHO + CO2 + NH4+ + Cl- |
|
| (amino acids) |
(chloramines) |
(aldehydes) |
|
| Nitrogen radical generation and secondary reactions |
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| Nitric oxide synthetase: |
arginine + O2 + NADPH |
→ |
NO• + citrulline + NADP+ |
| NO• + O2•- |
→ |
ONOO- (peroxynitrite) |
|
| ONOO- + H+ |
→ |
ONOOH (peroxynitrous acid) |
|
| ONOOH (peroxynitrous acid) |
→ |
NO3- (nitrate ion) |
|
| ONOOH |
→ |
NO2+ (nitronium ion) |
|
| ONOOH |
→ |
NO2• (nitrogen dioxide radical) |
|
| ONOOH |
→ |
OH- |
|
| ONOOH |
→ |
OH• (hydroxyl radical) |
|
| Lipid peroxidation |
|||
| LH + Radical• |
→ |
L• + RH |
|
| L• + O2 |
→ |
LOO• (lipid peroxyl radical) |
|
| LH + LOO• |
→ |
L• + LOOH (leading to lipid propagation) |
|
| LOO• + TocOH (α-tocopherol) |
→ |
LOOH + TocO• (chain termination) |
|
|
|
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|
Hitchon and El-Gabalawy Arthritis Res Ther 2004 6:265 doi:10.1186/ar1447 |
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