The Adriamycin (doxorubicin)-induced inactivation of cytochrome c oxidase depends on the presence of iron or copper.

1. It was confirmed that Adriamycin (doxorubicin) inactivates cytochrome c oxidase upon incubation. However, further investigation shows that this inactivation is strongly dependent upon the presence of Fe3+ and Cu2+. Trace amounts of these transition metal ions, present in phosphate and Tris buffers, bind strongly to the Adriamycin and the complex formed is responsible for the inactivation of cytochrome c oxidase. No Adriamycin-induced inactivation of cytochrome c oxidase occurred in the presence of EDTA or in phosphate buffers purified on a cation exchange column to remove trace metals. 2. The metal ion-induced inactivation of cytochrome c oxidase by Adriamycin results in significant decreases in both the maximum velocity and the Michaelis constant. The degree of inactivation is strongly dependent on the Fe3+ concentration. 3. Cardiolipin partially protects against cytochrome c oxidase inactivation, presumably by binding to the cytochrome c oxidase, whereas catalase or superoxide dismutase partially protect by scavenging damaging reactive oxygen species generated within a Fe3+-Adriamycin-enzyme complex.