Histoenzymological study of selected dehydrogenase enzymes in Pneumocystis carinii

The metabolic activity of Pneumocystis carinii cysts was studied histochemically by a tetrazolium dye technique to assess substrate-specific dehydrogenase activity. Lactate dehydrogenase, succinate dehydrogenase, and glutamate dehydrogenase produced moderate-to-strong reactions in the cysts, whereas glucose-6-phosphate dehydrogenase had little if any reactivity. These results suggest that pneumocystis cysts have some of the enzymes necessary for glycolysis, Krebs cycle activity, and intermediary protein metabolism. These studies provide a method of directly assessing metabolic pathways in P. carinii which circumvents the uncertainties of specificity inherent in previous investigations with partially purified suspensions.