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.

O-hexyl O-2,5-dichlorophenyl phosphoramidate as a substrate for domestic and sea bird serum A-esterases: Hydrolysis levels, Cu2+- and Zn2+-dependence and stereoselectivity.

O-Hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) induces delayed neuropathy in hens. It has been used as a tool to identify new A-esterase activities in animal tissues. This study shows the EDTA-resistant, Cu2+- and Zn2+-dependent hydrolysis of racemic HDCP in domestic and sea bird serum using UV/Vis spectrophotometry and chiral chromatography. The results clearly show a significant (p ˂ 0.05) Cu2+- and Zn2+-dependent HDCP hydrolysis in the serum of all bird species versus EDTA, except for the Zn2+-dependent HDCPase activity from Yucatecan quail serum. The ratio of Cu2+/Zn2+ hydrolysis varied between 1 and 7 (intraspecies) and 15.6 (interspecies). EDTA affected the Cu2+- and Zn2+-dependent HDCPase activity in the range of 37-95% and 40-50%, respectively. HDCP hydrolysis activated by Cu2+ was significantly (p ˂ 0.05) stereoselective (R-(+)-HDCP ˃ S-(-)-HDCP) in chicken and sea bird serum. Its R-(+)-HDCP/S-(-)-HDCP ratios were 6.8 and 1.6-2.8, respectively. EDTA-resistant and zinc-dependent HDCP hydrolysis were not stereospecific in all bird sera tested. The present ex vivo study reinforces the idea that bird sera have HDCPase activity that is sensitive to divalent metals, resistant to EDTA and possibly associated with the protein albumin.