Demonstration of glycosomes (microbodies) in the Bodonid flagellate Trypanoplasma borelli (Protozoa, Kinetoplastida).

Homogenates of Trypanoplasma borelli were subjected to subcellular fractionation by sequential differential and isopycnic centrifugation in sucrose. Glycerol-3-phosphate dehydrogenase and the glycolytic enzymes, glucosephosphate isomerase and triosephosphate isomerase, as well as the peroxisomal marker enzyme catalase were mainly, or in part, associated with sedimentable particles that had a buoyant density in sucrose of 1.22 g cm-3. Moreover, triosephosphate isomerase exhibited latency, both in total homogenates and in the particulate fraction. Electron microscopy of thin sections of T. borelli revealed the presence of microbodies that gave a positive reaction for catalase. Pyruvate kinase behaved as a typical soluble enzyme. It was stimulated by micromolar concentrations of fructose 2,6-bisphosphate and this stimulation was counteracted by inorganic phosphate in the millimolar range. The enzymes involved in the synthesis and degradation of fructose 2,6-bisphosphate, 6-phosphofructo-2-kinase and fructose-2,6-bisphosphatase, were both present in T. borelli and behaved as soluble enzymes. We conclude that in T. borelli the glycolytic pathway is compartmentalized in a way similar to that found in another Kinetoplastid family, the Trypanosomatidae, where seven glycolytic enzymes and two enzymes of glycerol metabolism are associated with glycosomes. Apparently the presence of glycosomes is a characteristic of all Kinetoplastida.