Respiratory systems in the Trypanosomidae

Abstract

Cell-free preparations from blood-stream trypanosomes of the brucei group contain a cytoplasmic L-[alpha]-glycerophosphate dehydrogenase and a particulate hydrogen-transport system whose rate of reaction with L-[alpha]-glycerophosphate was about 20 times that of reduced pyridine nucleotide or succinate. The reaction of the L-[alpha]-glycerophosphate-oxidase system with O2 was insensitive to both cyanide (0.5 m[image]) and antimycin A (5 [mu]g/ml). Cell-free preparations from blood-stream forms of Trypanosoma congolense, Trypanosoma lewisi and Trypanosoma vivax oxidize [alpha]-glycerophosphate, succinate and reduced diphosphopyridine nucleotide at about the same rate. The oxidation of these substrates by preparations of Trypanosoma lewisi was inhibited to about the same extent by cyanide (0.5 m[image]). Antimycin A (5 [mu]g/ml) was also an inhibitor. The ratio of the rates of O2 uptake by cell free preparations of the culture forms of Trypanosoma rhodesiense, Trypanosoma gambiense, Trypanosoma cruzi, Strigomonas oncopelti and Leishmania donovani was about 1:2:5 for [alpha]-glycerophosphate, succinate and reduced diphosphopyridine nucleotide respectively. [alpha]-Glycerophosphate- and succinic-oxidase activity in the 1st 3 of these species was inhibited by cyanide and antimycin A. In contrast, the oxidation of reduced diphosphopyridine nucleotide was slightly stimulated by these reagents. L-[alpha]-Glycerophosphate- and succinic-dehydrogenase activities were measured with phenazine methosulphate as electron acceptor in particulate preparations obtained from freeze-dried samples of both blood-stream and culture forms.