title: Inhibition by suramin of oxidative phosphorylation in Crithidia fasciculata.
abstract: 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.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D003421:Crithidia / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D009840:Oligomycins / Q000494:pharmacology; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010101:Oxygen Consumption; D013498:Suramin / Q000494:pharmacology*
chemical_list: D009840:Oligomycins; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D013498:Suramin; D000251:Adenosine Triphosphatases