Kelner M J, Bagnell R, Hale B, Alexander N M
Department of Pathology, University of California, San Diego 92103.
Arch Biochem Biophys. 1988 May 1;262(2):422-6. doi: 10.1016/0003-9861(88)90393-1.
Methylene blue competes 100 to 600 times more effectively than paraquat for reduction by three different flavo-containing enzymes; xanthine oxidase, NADH cytochrome c reductase, and NADPH cytochrome c reductase. Paraquat and methylene blue both interact with deflavo xanthine oxidase, indicating that neither electron acceptor reacted at the FAD site of the enzyme where molecular oxygen is reduced to superoxide. As the paraquat radical also directly reduced acetylated cytochrome c the hemeprotein could not be utilized for measuring superoxide production in the presence of the herbicide. In the presence of cytochrome c the methylene blue caused a sharp decrease in both paraquat-induced superoxide and hydroxyl radical production.
亚甲蓝在被三种不同的含黄素酶（黄嘌呤氧化酶、NADH 细胞色素 c 还原酶和 NADPH 细胞色素 c 还原酶）还原时，其竞争能力比百草枯强 100 至 600 倍。百草枯和亚甲蓝都与脱黄素黄嘌呤氧化酶相互作用，这表明两种电子受体都不在该酶的 FAD 位点反应，在该位点分子氧被还原为超氧化物。由于百草枯自由基也能直接还原乙酰化细胞色素 c，因此在除草剂存在的情况下，不能利用血红蛋白来测量超氧化物的产生。在细胞色素 c 存在的情况下，亚甲蓝使百草枯诱导的超氧化物和羟基自由基的产生都急剧减少。
