AFFINITY AND PHOSPHORYLATION CONSTANTS OF A SERIES OF O,O-DIALKYL MALAOXONS AND PARAOXONS WITH ACETYLCHOLINESTERASE

The affinity constants (Ka) and the phosphorylation constants (kp) were determined for a series of O,O-dialkyl malaoxons and paraoxons in which the phosphorylalkoxy groups were varied from methyl to butyl. The kp values of the di-n-alkyl malaoxons and paraoxons ranged from 43 to 67 min-1 except for di-n-butyl malaoxon which was only 25 min-1. Neither chain length nor leaving group appeared to affect kp greatly, although there were minor variations. Members in the paraoxon series bound better in each case than the comparable member of the malaoxon series. The Ka values were from two to ten times better for the paraoxon series than the comparable member of the malaoxon series. These values imparted the larger bimolecular rate constants to the paraoxon series. With di-i-propyl malaoxon and paraoxon poor binding occurred as well as a dramatic decrease in kp (3 min-1). © 1969.