The purification of the enzyme hydrolysing diethyl p-nitrophenyl phosphate (paraoxon) in sheep serum

Aldridge (1953b) reported an enzyme in mammalian sera which hydrolysed the acetyl¢holinesterase inhibitor, diethyl p-nitrophenyl phosphate (para- oxon) to diethylphosphoric acid and p-nitrophenol.No serious attempts have previously been made to purify this enzyme either from serum or from other tissues.Aldridge (1953b) fractionated rabbit serum with ammonium sulphate, but none of the fractions showed significant purification.In addition he showed that the Cohn et al. (1950) method 10 precipitated the enzyme in the (I + II + III) fraction.The yield was 85% and purification