SCHISTOSOMA-MANSONI SPOROCYSTS CONTAIN RHODOQUINONE AND PRODUCE SUCCINATE BY FUMARATE REDUCTION

Although schistosomes were thought to be one of the few parasitic helm inths that do not produce succinate via fumarate reduction, it was rec ently demonstrated that sporocysts of Schistosoma mansoni produce, und er certain conditions, succinate in addition to lactate. This succinat e production was only observed when the respiratory chain activity of the sporocysts was inhibited, which suggested that succinate is produc ed by fumarate reduction. In this report the presence of essential com ponents for fumarate reduction was investigated in various stages of S . mansoni and it was shown that, in contrast to adults, sporocysts con tained a substantial amount of rhodoquinone which is essential for eff icient fumarate reduction in eukaryotes. This rhodoquinone was not mad e by modification of ubiquinone obtained from the host, but was synthe sized de novo. Furthermore, it was shown that complex II of the electr on-transport chain in schistosomes has the kinetic properties of a ded icated fumarate reductase instead of those of a succinate dehydrogenas e. The presence of such an enzyme, together with the substantial amoun ts of rhodoquinone, shows that in S. mansoni sporocysts succinate is p roduced via fumarate reduction. Therefore, the energy metabolism of sc histosomes does not differ in principle from most other parasitic helm inths, which are known to rely heavily on fumarate reduction.