CROSS-LINKED HEMOGLOBIN-SUPEROXIDE DISMUTASE-CATALASE SCAVENGES OXYGEN-DERIVED FREE-RADICALS AND PREVENTS METHEMOGLOBIN FORMATION AND IRON RELEASE

In this study, we prepared PolyHb-SOD-catalase (intermolecularly cross -linked hemoglobin, superoxide dismutase (SOD), and catalase). We foun d that PolyHb-SOD-catalase is effective in scavenging oxygen-derived f ree radicals. In the xanthine/xanthine oxidase system, the initial rat e of cytochrome c reduction was 2.13 +/- 0,26 nmoles cyt. c/min for Po lyHb alone. PolyHb- SOD-catalase reduced this to 0.56 +/- 0.08 nmoles cyt. c/min because of its ability to eliminate superoxide (O2-). Addit ion of PolyHb to 200 muM of hydrogen peroxide (H2O2), changed the H2O2 level slightly to 192 +/- 0.4 muM. Addition of PolyHb-SOD-catalase, o n the other hand, lower the level to 41 +/- 0.3 muM. Results also show that both effects were dependent on the concentration of SOD-catalase cross-linked with hemoglobin. Oxidative challenge with H2O2, resulted in minimal changes in the absorbance spectra of PolyHb-SOD-catalase. With PolyHb, there were spectral changes reflecting the formation of m ethemoglobin and heme degradation. Furthermore, the amount of iron rel eased, after incubation with 250 muM H2O2, was 6.8 +/- 1.8 mug/dl for PolyHb-SOD-catalase and 76.6 +/- 1.0 mug/dl for PolyHb. These results show that cross-linked SOD-catalase prevents oxidative reactions invol ving the hemoglobin component of PolyHb-SOD-catalase.