Triphosphoinositide phosphodiesterase in a protozoan-crithidia. fasciculata

The hydrolysis of triphosphoinositide by a phosphodiesterase has been demonrated in a species of Trypanosomidae (Crithidia fasciculata). The activity in the crude homogenate was stimulated by K⁺, and diethyl ether or cetyltrimethylammonium bromide. The pH optimum was 7.0-7.2. The enzyme specifically required Ca²⁺ and was very sensitive to heat. The rate of triphosphoinositide hydrolysis at 25 °C was comparable to that reported for brain at 37 °C. Activity was associated with both the supernatant and particulate fractions. Phosphatidylinositol was not degraded and triphosphoinositide phosphomonoesterase activity was absent from homogenates prepared by grinding the protozoa with alumina.