METABOLIC DEACTIVATION OF THE HERBICIDE THIAZOPYR BY ANIMAL LIVER ESTERASES

1. Thiazopyr was hydrolysed in vitro to its corresponding acid by rabb it and porcine liver esterases. 2. A wide range of thiazopyr esterase activity was observed in extracts from liver acetone powders from 15 a nimal species with bovine, rabbit and pigeon showing the highest activ ities. 3. Using soybean tissue culture cells and Arabidopsis seedlings , the acidic metabolite was shown to possess <1% of the herbicidal act ivity of thiazopyr. 4. We propose that biotransformation of thiazopyr to the acid is a critical pathway of metabolism in animals and plants.