Hydrogen peroxide-mediated Cu,Zn-superoxide dismutase fragmentation: protection by carnosine, homocarnosine and anserine.

The fragmentation of human Cu,Zn-superoxide dismutase (SOD) was observed during incubation with H(2)O(2). Hydroxyl radical scavengers such as sodium azide, formate and mannitol protected the fragmentation of Cu,Zn-SOD. These results suggested that *OH was implicated in the hydrogen peroxide-mediated Cu,Zn-SOD fragmentation. Carnosine, homocarnosine and anserine have been proposed to act as anti-oxidants in vivo. We investigated whether three compounds could protect the fragmentation of Cu,Zn-SOD induced by H(2)O(2). The results showed that carnosine, homocarnosine and anserine significantly protected the fragmentation of Cu,Zn-SOD. All three compounds also protected the loss of enzyme activity induced by H(2)O(2). Carnosine, homocarnosine and anserine effectively inhibited the formation of *OH by the Cu,Zn-SOD/H(2)O(2) system. These results suggest that carnosine and related compounds can protect the hydrogen peroxide-mediated Cu,Zn-SOD fragmentation through the scavenging of *OH.