Figure 4.

Effect of cardiolipin on the degradation of cytochrome c. 15 μm cyt c was incubated in the absence or presence of 1.5 mm liposomes with up to 500 μm H₂O₂ in 10 mm PB, pH 7.4, at 37 °C for up to 3 h. As shown in A, both in the absence of lipid (black) and in the presence of PLPC (green) in the absence of H₂O₂ (dashed) no heme degradation occurs, whereas in the presence of H₂O₂ (75 μm; straight) a small heme loss takes place. With TOCL (blue) in the presence of H₂O₂ comparable heme degradation is observed with a faster kinetics. After preincubation with TLCL (red) even in the absence of H₂O₂ a quick and more substantial heme degradation takes place that, in the additional presence of H₂O₂, leads to a complete heme loss. In B, the k_obs value obtained from the linear phase of the Soret band decrease is replotted against the H₂O₂ concentration and always exhibits a linear relationship. As shown in C, from the corresponding slopes, k₂ values for the H₂O₂-derived heme degradation were calculated, showing considerably higher values in the presence of CL-containing liposomes. In A, averaged kinetic curves from three independent measurements are shown; in B and C, the corresponding mean (columns) and S.D. (error bars) values are shown.