Liposome-recruited activity of oxidized and fragmented superoxide dismutase

The peptide fragment of H₂O₂-treated Cu,Zn-superoxide dismutase (SOD) was found to be reactivated with liposomes prepared by l-palmitoyl-2-oleoyl-.m-glycero-3-phosphocholine (POPC). The fragmentation of SOD was observed by 2 mM H₂O₂ treatment as well as by SOD inactivation and the loss of an α-helix in the neighborhood of its activity center. The H₂O₂-treated SOD, which lost its activity at different incubation times, was dramatically reactivated only by adding POPC liposomes, resulting in 1.3-2.8 times higher enzymatic activity. The ultrafiltration analysis of H₂O₂-treated SOD co-incubated with liposomes shows that some specific peptide fragments of the oxidized SOD can interact with POPC liposomes. A comparison of the fractions detected in reverse-phase chromatography shows that specific SOD fragments are able to contribute to the reactivation of oxidized and fragmented SOD in the presence of POPC liposomes. The liposomes can recruit the potentially active fragment of SOD among the lethally damaged SOD fragments to elucidate the antioxidative function.