[Acetylcholinesterase of cobra venom. Determination of concentration of active sites].

O-Nitrophenyl dimethylcarbamate and organophosphorus inhibitors O-n-propyl-p-nitrophenyl methylphosphonate, O-n-butyl-p-nitrophenyl methylphosphonate, O,O-diethyl-p-nitrophenyl phosphate, O-n-butyl-S-(beta-ethylmercaptoethyl) methylthiophosphonate, methysulphate of O,O-diethyl-S-(beta-phenyldimethylammoniumethly) thiophosphate were used in the titration of acetylcholinesterase active site concentratration in Naja naja oxiana venom. No side reactions with the acetylcholinesterase molecule as well as with other components of the venom were observed. In titration the effective concentrations of organophosphorus inhibitors with asymmetric phosphorus were 50% of their analytical concentrations, since cobra venom cholinesterase showed practically absolute stereoselectivity against the compounds.