Winterbourn C C
Biochem Int. 1983 Jul;7(1):1-8.
Paraquat radicals generated with xanthine oxidase in N2 reduced methemoglobin to deoxyhemoglobin. In air, reduction to oxyhemoglobin occurred but at one third the rate. In air the reaction was 10 times faster and gave greater overall reduction to oxyhemoglobin than with O2 generated at a similar rate. Aerobic methemoglobin reduction in the presence of paraquat was inhibited by superoxide dismutase. It is concluded that paraquat radicals reduce methemoglobin directly in air and that this reaction must be very fast with a rate constant of the order of 10(9) M-1 s-1. This is an example where paraquat radicals in air do not all react with O2. It cannot therefore be assumed that the radical reactions of paraquat in air are due solely to O2 and its products.
用黄嘌呤氧化酶在氮气中产生的百草枯自由基将高铁血红蛋白还原为脱氧血红蛋白。在空气中，可发生向氧合血红蛋白的还原，但速率仅为前者的三分之一。在空气中，该反应比以类似速率产生的氧气快10倍，且对氧合血红蛋白的总体还原程度更高。超氧化物歧化酶可抑制百草枯存在时的需氧高铁血红蛋白还原。结论是，百草枯自由基在空气中直接还原高铁血红蛋白，且该反应必定非常迅速，速率常数约为10(9) M-1 s-1。这是一个空气中的百草枯自由基并非都与氧气反应的例子。因此，不能假定百草枯在空气中的自由基反应仅归因于氧气及其产物。
