STUDIES ON SUCCINOXIDASE OF SCHISTOSOMA JAPONICUM
摘要
Activities of succinoxidase, succinic dehydrogenase, succinic-cytochrome c reductase and cytochrome oxidase in homogenates of Schistosoma japonicum were demonstrated manometrically and spectrophotometrically. It was observed that the succinoxidase activity was directly proportional to the concentration of cytochrome c from 0.4×10~(-5)M to 2×10~(-5)M. The enzymic activity was also closely related to the phosphate concentration, the lower the concentration, the higher the activity. The activity of succinoxidase in the homogenate of S. japonicum was determined under its optimal conditions(succinate, 0.02M; cytochrome c, 2×10~(-5)M; phosphate buffer, 0.01M, pH 7.4). The values of paired worms were shown as follows: oxygen uptake, Q_(O_2)=30.3μl/hr./mg.N; succinate consumption, Q_S=322μg./hr./mg.N; fumarate production, Q_F=157μg./hr./mg.N. On the basis of mg. of nitrogen, the activity of the female worms was found to be higher than that of the male worms. Malonate, diethyldithiocarbamate and cyanide inhibited markedly the activity of succinoxidase, whereas tartar emetic, Sb-58 and Fouadin in the concentration of 2×10~(-3)M did not show any significant inhibitory effect. Furthermore, cyanide inhibited not only cytochrome oxidase, but also succinic dehydrogenase of S. japonicum as determined by the methylene blue method. It was found that Menadione(vitamin K_3) was able to stimulate the oxygen uptake temporarily, when succinate was used as the substrate. Preliminary results indicated that the homogenate of S. japonicum heated in boiling water bath for 30 minutes could liberate a thermo-stablereducing substance, which was capable of reducing cytochrome c anaerobically in the absence of succinate. The metabolism of succinate and the role of cytochrome system in S. japonicum were discussed.