Natella F, Nardini M, Ursini F, Scaccini C
Free Radical Research Group, National Institute of Nutrition, Rome, Italy.
Free Radic Res. 1998 Nov;29(5):427-34. doi: 10.1080/10715769800300471.
Heme-peroxidases, such as horseradish peroxidase (HRP), are among the most popular catalysts of low density lipoprotein (LDL) peroxidation. In this model system, a suitable oxidant such as H2O2 is required to generate the hypervalent iron species able to initiate the peroxidative chain. However, we observed that traces of hydroperoxides present in a fresh solution of linoleic acid can promote lipid peroxidation and apo B oxidation, substituting H2O2. Spectral analysis of HRP showed that an hypervalent iron is generated in the presence of H2O2 and peroxidizing linoleic acid. Accordingly, careful reduction of the traces of linoleic acid lipid hydroperoxide prevented formation of the ferryl species in HRP and lipid peroxidation. However, when LDL was oxidized in the presence of HRP, the ferryl form of HRP was not detectable, suggesting a Fenton-like reaction as an alternative mechanism. This was supported by the observation that carbon monoxide, a ligand for the ferrous HRP, completely inhibited peroxidation of LDL. These results are in agreement with previous studies showing that myoglobin ferryl species is not produced in the presence of phospholipid hydroperoxides, and emphasize the relevance of a Fenton-like chemistry in peroxidation of LDL and indirectly, the role of pre-existing lipid hydroperoxides.
血红素过氧化物酶，如辣根过氧化物酶（HRP），是低密度脂蛋白（LDL）过氧化反应中最常用的催化剂之一。在这个模型系统中，需要一种合适的氧化剂，如过氧化氢（H2O2）来生成能够引发过氧化链式反应的高价铁物种。然而，我们观察到在新鲜的亚油酸溶液中存在的痕量氢过氧化物可以促进脂质过氧化和载脂蛋白B氧化，从而替代H2O2。HRP的光谱分析表明，在H2O2和过氧化亚油酸存在的情况下会生成高价铁。因此，仔细还原亚油酸脂质氢过氧化物的痕量可以防止HRP中高铁物种的形成和脂质过氧化。然而，当LDL在HRP存在下被氧化时，未检测到HRP的高铁形式，这表明类似芬顿反应是一种替代机制。一氧化碳是亚铁HRP的配体，它完全抑制LDL的过氧化，这一观察结果支持了这一点。这些结果与先前的研究一致，先前的研究表明在磷脂氢过氧化物存在的情况下不会产生肌红蛋白高铁物种，并强调了类似芬顿化学在LDL过氧化中的相关性，以及间接强调了预先存在的脂质氢过氧化物的作用。
