In trypanosomatid cytochrome c, contrary to the cyt c of other organisms, the haem is is attached by one rather than by two cysteines to the protein. The presence of cytochrome o has also been reported. In these trypanosomatids mitochondrial activity can be completely suppressed. Cytochromes then are absent and respiration becomes insensitive to cyanide andthe citric-acid cycle enzymes cannot be detected. Under these conditions the organisms utilise mainly carbohydrates for their energy generation and glycolysis is the main or only energy-generating pathway.
Mitochondrial activity is required for the passage through the insect vector.
In the fly midgut carbohydrates are scarce or absent, but the concentration of amino-acids that are generated by digestion of blood proteins are abundantly present. Oxidation of amino acids requires the enzymes of the citric-acid cycle and a functional respiratory chain. The kinetoplast DNA or kDNA is present in a specialised region of the mitochondrion, called the kinetoplast. This kinetoplast is always afound at the place of entry into the cell of the flagellum and is opposed to the basal body of the latter. The latter is the equivalent of the classical mitochondrial genome of other organisms and contains a number of genes coding for some of the components of the mitochondrial respiratory chain.