Inhibition by suramin of oxidative phosphorylation in Crithidia fasciculata

• Published in: Comparative biochemistry and physiology. B, Comparative biochemistry Vol. 71; no. 4; p. 611
• Main Authors: Roveri, O A, Franke de Cazzulo, B M, Cazzulo, J J
• Format: Journal Article
• Language: English
• Published: England 1982
• Subjects: Adenosine Triphosphatases - metabolism; Animals; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - pharmacology; Crithidia - drug effects; Crithidia - metabolism; Kinetics; Oligomycins - pharmacology; Oxidative Phosphorylation - drug effects; Oxygen Consumption; Suramin - pharmacology
• ISSN: 0305-0491
• DOI: 10.1016/0305-0491(82)90470-9

1. The ADP plus Pi-stimulated oxidation of succinate by mitochondria from the insect trypanosomatid Crithidia fasciculata was maximally inhibited (64%) by suramin at a concentration (60 microM) which did not affect the electron transport uncoupled by FCCP. Inhibition of the latter required a considerably higher concentration of the drug, 50% inhibition being attained at about 0.8 mM. 2. ATP synthesis by mitochondrial particles was inhibited by suramin, 50% inhibition being attained at about 50 microM. This inhibition was strictly competitive towards ADP, but it was not linearly competitive, since a secondary plot of apparent Km values vs concentration of the drug was strongly concave upwards. 3. The FCCP-stimulated ATPase activity of the mitochondrial particles was completely abolished either by oligomycin (20 micrograms/ml) or by 200 microM suramin. 4. The results suggest that oxidative phosphorylation may be a primary target for the trypanocide effect of suramin on organisms having, like C. fasciculata, a well-developed respiratory chain.