CuZn superoxide dismutase activities from Fasciola hepatica

The levels of superoxide dismutase (SOD) were determined in detergent-solub le, somatic and excretion-secretion (E-S) preparations from adult Fasciola hepatica using the xanthine oxidase system and visualized in substrate gels . Compared to detergent-soluble and somatic extracts, E-S products showed t he highest SOD activity (88.5 U/mg), indicating active release to the mediu m in which parasites were maintained. SOD specific activity was also detect ed at high levels in E-S products from 3-week-old and 5-week-old immature m igrating flukes (25 and 143 U/mg, respectively). In all preparations except for the somatic extract, the activity was characterized as cyanide-sensiti ve CuZn SOD. Differences in SOD isoenzyme profiles between the extracts wer e observed in native polyacrylamide gel electrophoresis: the somatic and de tergent-soluble extracts exhibited 1 band of activity while the E-S product s from immature and adults flukes contained 2 and 3 migrating bands, respec tively. SOD was purified from the detergent-soluble extract and E-S product s of adult worms by a combination of ultrafiltration, gel filtration on Sep hacryl S-200 HR and ion-exchange chromatography on QAE Sephadex A-50. The S OD from detergent-soluble extract showed, by SDS-PAGE analysis, 1 band of 1 6 kDa apparent molecular weight. The SOD from E-S products showed 2 bands o f 16 and 60 kDa apparent molecular weight. N-terminal sequence analysis of the 16 kDa band from the detergent-soluble preparation showed some similari ty with Schistosoma mansoni cytoplasmic SOD. These enzymes may have a poten tial role in the evasion of the oxidative burst killing mechanism by immune cells.