Belikova Natalia A, Tyurina Yulia Y, Borisenko Grigory, Tyurin Vladimir, Samhan Arias Alejandro K, Yanamala Naveena, Furtmüller Paul Georg, Klein-Seetharaman Judith, Obinger Christian, Kagan Valerian E
Center for Free Radical and Antioxidant Health and Department of Environmental and Occupational Health, University of Pittsburgh, 100 Technology Drive, Suite 350, Pittsburgh, Pennsylvania 15219-3130, USA.
J Am Chem Soc. 2009 Aug 19;131(32):11288-9. doi: 10.1021/ja904343c.
Cytochrome c (cyt c), a mitochondrial intermembrane electron shuttle between complexes III and IV, can, upon binding with an anionic phospholipid, cardiolipin (CL), act as a peroxidase that catalyzes cardiolipin oxidation. H(2)O(2) was considered as a source of oxidative equivalents for this reaction, which is essential for programmed cell death. Here we report that peroxidase cyt c/CL complexes can utilize free fatty acid hydroperoxides (FFA-OOH) at exceptionally high rates that are approximately 3 orders of magnitude higher than for H(2)O(2). Similarly, peroxidase activity of murine liver mitochondria was high with FFA-OOH. Using EPR spin trapping and LC-MS techniques, we have demonstrated that cyt c/CL complexes split FFA-OOH predominantly via a heterolytic mechanism, yielding hydroxy-fatty acids, whereas H(2)O(2) (and tert-butyl hydroperoxide, t-BuOOH) undergo homolytic cleavage. Computer simulations have revealed that Arg(38) and His(33) are important for the heterolytic mechanism at potential FFA-OOH binding sites of cyt c (but not for H(2)O(2) or t-BuOOH). Regulation of FFA-OOH metabolism may be an important function of cyt c that is associated with elimination of toxic FFA-OOH and synthesis of physiologically active hydroxy-fatty acids in mitochondria.
细胞色素c（cyt c）是一种位于线粒体膜间隙、在复合物III和IV之间穿梭的电子载体，与阴离子磷脂心磷脂（CL）结合后，可作为一种过氧化物酶催化心磷脂氧化。H₂O₂被认为是该反应的氧化当量来源，这对程序性细胞死亡至关重要。在此我们报告，过氧化物酶细胞色素c/心磷脂复合物能够以极高的速率利用游离脂肪酸氢过氧化物（FFA-OOH），其速率比利用H₂O₂时高出约3个数量级。同样，小鼠肝脏线粒体对FFA-OOH的过氧化物酶活性也很高。利用电子顺磁共振自旋捕获和液相色谱-质谱技术，我们证明细胞色素c/心磷脂复合物主要通过异裂机制分解FFA-OOH，生成羟基脂肪酸，而H₂O₂（以及叔丁基过氧化氢，t-BuOOH）则发生均裂。计算机模拟显示，在细胞色素c潜在的FFA-OOH结合位点处，精氨酸（Arg38）和组氨酸（His33）对异裂机制很重要（但对H₂O₂或t-BuOOH不重要）。FFA-OOH代谢的调节可能是细胞色素c的一项重要功能，这与线粒体中有毒FFA-OOH的清除以及生理活性羟基脂肪酸的合成有关。
