Cu2+-dependent stereoselective hydrolysis of a chiral organophosphonothioate insecticide for domestic mammals' sera and its albumins.

Acute toxicity of organophosphate (OPs) pesticides is a public health problem. The adverse effects are associated with the inhibition and aging of nervous system B-esterases such as acetyl cholinesterase (AChE) and neuropathic target esterase (NTE). Treatment based on A-esterases such as mammal serum paraoxonase-1 has been suggested. This ex vivo study shows the Cu2+-dependent hydrolysis of trichloronate (TCN), a racemic organophosphonothioate insecticide, in human and domestic mammal serum (dog, goat, pig, sheep and cow). Ca2+-dependent (2.5 mM) or EDTA-resistant (5 mM) activity (1-6%) was not significant (p>0.05) in all samples, except goat serum and its albumin, which showed higher levels of TCN hydrolysis (38-58%) than other mammals with 100 and 300 μM copper sulfate at physiological conditions for 60 min. Goat serum albumin (GSA) showed significant (p˂0.05) stereoselective hydrolysis (+)-TCN ˃ (-)-TCN (45% versus 33%). This suggests that GSA is the protein responsible for Cu2+-dependent TCNase activity in goat serum. This is the first report on Cu2+-dependent A-esterase activity in mammalian tissues. This goat serum cuproprotein could be considered as an alternative in future biotechnological applications including enantiomeric synthesis, bioremediation and antidotal treatment of organophosphonothioate pesticide poisoning.