The inhibition by fluorocitrate of rat liver mitochondrial and extramitochondrial aconitate hydratase.
1. The effects of synthetic fluorocitrate were studied on: (a) the oxidation of citrate and cis-aconitate by rat liver mitochondria; (b) the activity of the aconitate hydratase found in the liver cell sap; (c) the activity of the aconitate hydratase solubilized from liver mitochondria. 2. Fluorocitrate was found to be a potent inhibitor of oxidation of citrate but only a weak inhibitor of oxidation of cis-aconitate: 6.7mum-fluorocitrate (containing 4% of the inhibitory isomer) caused 94% inhibition of the oxidation of citrate (2mm) whereas 1.0mm-fluorocitrate was necessary to provoke the same inhibition when cis-aconitate (2mm) was the substrate. The degree of inhibition varied in relation to the respiratory state of mitochondria when fluorocitrate was added. The inhibition could be partially reversed by cis-aconitate. 3. The aconitate hydratase extracted from the mitochondria was much less inhibited by fluorocitrate than was the mitochondria-bound enzyme, and the aconitate hydratase found in the cell sap was even less sensitive. 0.3mm-Fluorocitrate was required to cause 50% inhibition of the reaction citrate-->cis-aconitate, catalysed by the aconitate hydratase extracted from the mitochondria, and 1.2m-fluorocitrate for the extramitochondrial enzyme. For both enzymes the reaction citrate-->cis-aconitate was 2-3 times more sensitive to fluorocitrate than was the reaction isocitrate-->cis-aconitate. The inhibition was of the competitive type for both reactions.
D000818:Animals; D002498:Centrifugation; D002951:Citrates / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D005461:Fluorine / Q000494:pharmacology*; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology; D051381:Rats; D013386:Succinates
D002951:Citrates; D013386:Succinates; D005461:Fluorine; D006836:Hydro-Lyases
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