Remarkable activities of nucleoside triphosphate hydrolase in the tachyzoites of both virulent and avirulent strains of Toxoplasma gondii.

Dithiothreitol-dependent MgATP2- and Mg-ADP- hydrolytic activities owing to nucleoside triphosphate hydrolase were examined kinetically in tachyzoite cells of five strains of Toxoplasma gondii with various virulence. The tachyzoites of all the strains were revealed to have a high ATP and ADP hydrolytic potency. The value of Vmax and Km obtained from each strain indicated that there were two classified types of T. gondii about ATP and ADP hydrolysis. The most virulent strain (RH) and avirulent strain (Fukaya) were classified in a type with higher ATPase than ADPase activities. Two virulent strains (C56, Beverley) and an avirulent strain (ME49) were classified in the other type with the same activities of ATPase and ADPase.