Fine structure and cytochemistry of peroxisomes (microbodies) in Leptomonas samueli

Summary Leptomonas samueli possesses in its cytoplasm a membrane-bounded organelle which can reach a length of 2.8 m and a diameter of 0.2 m. Catalase activity, which is inhibited by 3-amino-1, 2, 4-triazole, was detected at the ultrastructural level in the matrix of the organelle by using an alkaline diaminobenzidine medium. Freeze-fracture studies showed the presence of a large number of intramembranous particles on both the P and the E faces of the membrane of the organelle. Based on these data as well as on previous observations, it is suggested that the trypanosomatids possess an organelle that can be considered to be a peroxisome.