Question

2. Some plants in Africa and Australia have been found to produce toxic fluorinated fatty acid derivatives such as w-Fluorooctadecanoic acid, as a defense mechanism against grazing by herbivores. Ingestion of these toxic compounds by livestock often results in fatal poisonings. The effects of w-Fluorooctadecanoic acid include: decreased rate of glycolysis accumulation of fructose 6-phosphate decreased concentration of all citric acid cycle intermediates except for citrate, with the concentration 10 times greater than normal. • Based on these observations, determine: a. Why did glycolysis decrease? Why did fructose 6-phosphate accumulate? (7pt) b. What caused citrate to accumulate and other cycle intermediates to be depleted? (5pt) c. Why is poisoning with fluorinated fatty acid derivatives fatal? (5pt)

Answer 1

Fluorinated fatty acid derivatives such as omega-fluorooctadecanoic acid and fluoroacetate. The fluorinated fatty acids releases fluoroacetyl coenzyme A that on entering citric acid cycle act as strong inhibitor of aconitase thus inhibiting citric acid cycle. Hence, poisoning with fluorinated fatty acids derivatives fatal.

The accumulation of citrate due to inhibition of aconitase causes toxicity due to reduction in ATP levels. Accumulated levels of citrate causes chelation of divalent cations, like Mg2+, Ca2+. This will affect the activities of other enzymes as well like phosphofructokinase. This will decrease the glycolysis.