The inhibition of plant aconitate hydratase (aconitase) by fluorocitrate.

Fluoroacetate is a potent poison of animals. It is metabolized to fluorocitrate, which is a powerful inhibitor of mammalian aconitate hydratase [aconitase; citrate (isocitrate) hydrolyase] (Peters, 1952). Fluoroacetate and fluoroacetamide, as systemic insecticides for plants, are taken up by the roots or absorbed by the leaves and are then translocated to other parts of the plant. The plants show signs of injury only at doses 50-100 times that needed to kill Aphis fabae when feeding on the plants (David & Gardiner, 1951). Two distinct species of plants synthesize fluoroacetate, namely Dichapetalum cymosum (Marais, 1944) and Acacia georgina (Oelrichs & McEwan, 1961; Murray, McConnell & Whittem, 1961). Dichapetalum toxicarium can synthesize w-fluoro-oleic acid (Peters, Hall, Ward & Sheppard, 1960). It is apparent that plants are much less sensitive to fluoroacetate than are animals. To ascertain a reason for the lower sensitivity of plants we have examined the inhibition of aconitate hydratase from plant sources; we find it to be much less strongly inhibited by fluorocitrate than is pig-heart aconitate hydratase (Peters, 1961).