Bodaness R S, Chan P C
J Biol Chem. 1977 Dec 10;252(23):8554-60.
The oxygen-dependent photooxidation of NADPH in the presence of hematoporphyrin in D2O results in the production of enzymatically active NADP+. The reaction is not inhibited by benzoate, mannitol, superoxide dismutase, or catalase. Moreover, addition of either potassium superoxide or H2O2 does not potentiate the reaction. This suggests OH-, H2O2, and O-2 are not likely to be the reactive oxygen species in this system. The oxidation is inhibited by various singlet oxygen quenchers and inhibitors such as 1,4-diazabicyclo[2.2.2]octane, 2,5-dimethylfuran plus methanol, histidine, and methionine. In addition, the rate of oxidation in H2O is less than one-fifth of that in D2O. The results suggest a singlet oxygen-mediated process. During the oxidation, no superoxide radical production could be detected with either ferricytochrome c or nitroblue tetrazolium. However, H2O2 has been found as one of the products. These observations are consistent with an oxidation-reduction reaction between singlet oxygen and NADPH to form H2O2 and NADP+, catalyzed by the light-activated photosensitizer hematoporphyrin.
在重水中，存在血卟啉的情况下，NADPH的氧依赖性光氧化作用会产生具有酶活性的NADP⁺。该反应不受苯甲酸盐、甘露醇、超氧化物歧化酶或过氧化氢酶的抑制。此外，添加超氧化钾或过氧化氢均不能增强该反应。这表明OH⁻、H₂O₂和O₂⁻不太可能是该体系中的活性氧物种。该氧化反应受到各种单线态氧猝灭剂和抑制剂的抑制，如1,4 - 二氮杂双环[2.2.2]辛烷、2,5 - 二甲基呋喃加甲醇、组氨酸和蛋氨酸。此外，H₂O中的氧化速率不到D₂O中氧化速率的五分之一。结果表明这是一个单线态氧介导的过程。在氧化过程中，用铁细胞色素c或硝基蓝四唑均检测不到超氧自由基产生。然而，已发现H₂O₂是产物之一。这些观察结果与单线态氧和NADPH之间的氧化还原反应一致，该反应在光激活的光敏剂血卟啉催化下形成H₂O₂和NADP⁺。
