Monroy-Noyola_2019_Chem.Biol.Interact_13ChEPon_310_108727

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, Cu(2+)- and Zn(2+)-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) Cu(2+)- and Zn(2+)-dependent HDCP hydrolysis in the serum of all bird species versus EDTA, except for the Zn(2+)-dependent HDCPase activity from Yucatecan quail serum. The ratio of Cu(2+)/Zn(2+) hydrolysis varied between 1 and 7 (intraspecies) and 15.6 (interspecies). EDTA affected the Cu(2+)- and Zn(2+)-dependent HDCPase activity in the range of 37-95% and 40-50%, respectively. HDCP hydrolysis activated by Cu(2+) 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.