The Binding Strength of Cytochrome <scp>C</scp> to Membranes Containing Phosphatidic Acid Corresponds to Its Peroxidase Activity

The study of the molecular mechanisms of programmed cell death and the role of anionic phospholipids like cardiolipin in these processes is one of the most attractive topics in modern lipidomics. The aim of this study was the quantitative assessment of the presence of phosphatidic acid in the binding strength of cytochrome C to biological membranes, its peroxidase activity, and the role of phospholipase D in increasing the concentration of phosphatidic acid. Using the Langmuir method for fluorescence quenching analysis (K _d = 2.78 × 10^-7 M) of the cytochrome C-phosphatidic acid complex was shown. The presence of phosphatidic acid (both synthetic and obtained from phosphatidylcholine using phospholipase D from mitochondrial lipids) increased the peroxidase activity of cytochrome C more than 100-fold (measured by luminol-enhanced chemiluminescence method). The obtained results emphasize the possibility of participation not only of cardiolipin but also of phosphatidic acid in the development of molecular proapoptotic processes.