[On kinetics of the paraoxon hydrolysing enzyme in human serum (EC 3.1.1.2) (author's transl)].

Human serum contains an enzyme which hydrolyses Paraoxon (E-600, an organic ester of phosphoric acid) by splitting of p-nitrophenol. This enzyme is very specific and shows a statistically significant polymorphism: I.e. in a normal population there are three groups with high, middle and low enzyme activity. The results presented in this paper confirm this polymorphism by showing a differing kinetic behaviour of the enzyme in the three groups. Paraoxon, methyl-paraoxon and chlor-methyl-paraoxon are most likely hydrolysed by the same enzyme and in the same way. On the other hand hydrolysation of n-propyl-paraoxon seems to be dependent on a different enzyme. A kompetitive inhibition of paraoxon-hydrolysation is exerted by S-substituted analogues of paraoxon. Paraoxon-hydrolysation is not influenzed by the addition of singly or doubly desalcylized derivatives of Paraoxon or compounds in which the nitro group is not in the p-position.