Plant Poisons and the Citric Acid Cycle

Plant Poisons and the Citric Acid Cycle

Another possible substrate for citrate synthase is fluoroacetyl-CoA. The source of the fluoroacetyl-CoA is fluoroacetate, which is found in the leaves of various types of poisonous plants, including locoweeds. Animals that ingest these plants form fluoroacetyl-CoA, which, in turn, is converted to fluorocitrate by their citrate synthase. Fluorocitrate, in turn, is a potent inhibitor of aconitase, the enzyme that catalyzes the next reaction of the citric acid cycle. These plants are poisonous because they produce a potent inhibitor of life processes.

The poison called Compound 1080 (pronounced “ten-eighty”) is sodium fluoroacetate. Ranchers who want to protect their sheep from attacks by coyotes put the poison just outside the ranch fence. When the coyotes eat this poison, they die. The mechanism of poi-soning by Compound 1080 is the same as that by plant poisons.