Figure 2.

Effect of cardiolipin on cytochrome c peroxidase activity. After preincubating 5 μm cyt c in 10 mm PB, pH 7.4, with liposomes (500 μm lipid concentration) in 10 mm PB, pH 7.4, 50 μm H₂O₂ was added, and the formation of ABTS^+• from 1 mm ABTS was followed for up to 3 h at 37 °C by monitoring the absorbance increase at 734 nm. The kinetic curves in A show that PLPC (green) has no effect on the cyt c–based peroxidase activity either in the presence (straight line) or in the absence (dashed line) of H₂O₂. TOCL (blue) strongly promotes the H₂O₂-derived cyt c–based peroxidase activity. TLCL (red) also supports the H₂O₂-derived cyt c peroxidase activity promotion but also activates this enzymatic activity on its own. In B, the H₂O₂-derived increase in the peroxidase activity of cyt c is shown for the lipid-free system (black) as well as for liposomes with the named lipids. In A, averaged kinetic curves from three independent experiments are shown; in B, the corresponding mean (columns) and S.D. (error bars) values are given.