Liochev S, Fridovich I
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
Arch Biochem Biophys. 1988 Jun;263(2):299-304. doi: 10.1016/0003-9861(88)90639-x.
Vandate augments the oxidation of NAD(P)H, but not of NMNH, by rat liver microsomes. Paraquat increases the vanadate effect on NADPH, but not on NADH, oxidation. Substoichiometric levels of NADPH caused the co-oxidation of NADH or NMNH and SOD inhibited in all cases. The ratio of NADH or NMNH co-oxidized per NADPH added allowed estimation of average chain length, which increased as the pH was lowered from 8.0 to 7.1. The initial rate of this co-oxidation of NMNH was a saturating function of the concentration of microsomes, reflecting a decrease in chain length with an increase in number of concomitant reaction chains, and due to increasing radical-radical termination reactions. Mitochondrial outer membranes behaved like the microsomal membranes, but mitochondrial inner membranes catalyzed a rapid oxidation of NADH which could be augmented by vanadate, whose action was enhanced by paraquat and inhibited by antimycin or rotenone. These and related observations support the view that vanadate stimulates NAD(P)H oxidation by biological membranes, not by virtue of interacting with enzymes, but rather by interacting with O-2.
钒酸盐可增强大鼠肝微粒体对NAD(P)H的氧化作用，但对NMNH无此作用。百草枯可增强钒酸盐对NADPH氧化的作用，但对NADH氧化无此作用。亚化学计量水平的NADPH会导致NADH或NMNH的共氧化，且在所有情况下超氧化物歧化酶（SOD）均受到抑制。每添加一分子NADPH所共氧化的NADH或NMNH的比例可用于估算平均链长，该链长会随着pH值从8.0降至7.1而增加。NMNH这种共氧化的初始速率是微粒体浓度的饱和函数，这反映出随着伴随反应链数量的增加链长会缩短，这是由于自由基 - 自由基终止反应增加所致。线粒体外膜的表现与微粒体膜相似，但线粒体内膜可催化NADH的快速氧化，钒酸盐可增强这种氧化作用，百草枯可增强钒酸盐的作用，而抗霉素或鱼藤酮可抑制其作用。这些以及相关的观察结果支持这样一种观点，即钒酸盐通过与生物膜相互作用而非与酶相互作用来刺激NAD(P)H的氧化，而是通过与O₂相互作用来实现的。
