Characterisation of Fasciola hepatica cytochrome c peroxidase as an enzymewith potential antioxidant activity in vitro

Cytochrome c peroxidase oxidises hydrogen peroxide using cytochrome c as th e electron donor. This enzyme is found in yeast and bacteria and has been a lso described in the trematodes Fasciola hepatica and Schistosoma mansoni. Using partially purified cytochrome c peroxidase samples from Fasciola hepa tica we evaluated its role as an antioxidant enzyme via the investigation o f its ability to protect against oxidative damage to deoxyribose in vitro. A system containing Fe-III-EDTA plus ascorbate was used to generate reactiv e oxygen species superoxide radical, H2O2 as well as the hydroxyl radical. Fasciola hepatica cytochrome c peroxidase effectively protected deoxyribose against oxidative damage in the presence of its substrate cytochrome c. Th is protection was proportional to the amount of enzyme added and occurred o nly in the presence of cytochrome c. Due to the low specific activity of th e final partially purified sample the effects of ascorbate and calcium chlo ride on cytochrome c peroxidase were investigated. The activity of the part ially purified enzyme was found to increase between 10 and 37% upon reducti on with ascorbate, However, incubation of the partially purified enzyme wit h 1 mM calcium chloride did not have any effect on enzyme activity. Our results showed that Fasciola hepatica CcP can protect deoxyribose from oxidative damage in vitro by blocking the formation of the highly toxic hyd roxyl radical (. OH). We suggest that the capacity of CcP to inhibit . OH-f ormation, by efficiently removing H2O2 from the in vitro oxidative system, may extend the biological role of CcP in response to oxidative stress in Fa sciola hepatica. (C) 1999 Australian Society for Parasitology. Published by Elsevier Science Ltd. All rights reserved.