Reaction of S-(?-ethylmercaptoalkyl) diphenyl thiophosphinates, O-(?-ethylmercaptoalkyl) diphenyl phosphinates, and their methiodides with cholinesterase from horse blood serum

Abstract

1. We determined the kinetic constants for the combined inhibition of butyrylcholinesterase by diphenyl thiophosphinates (C6H5)2P(O)S(CH2)nSC2H5 and their methiodides\((C_6 H_5 )_2 P(O)S(CH_2 )n\mathop S\limits^ \oplus (CH_3 )C_2 H_5 \cdot I^-- \), with n=2–6, and also the reversible inhibition constants for the analogous oxygen esters. 2. The ability of diphenyl thiophosphinates, diphenyl phosphinates, and their methiodides, to undergo reversible sorption on the active surface of the enzyme is enhanced with increase in the number of CH2 groups. In the sulfide series of thioesters the irreversible inhibition rate constants remain practically unchanged with increase in the number of CH2 groups, while in the sulfonium series they decrease symbatically with decrease in their alkaline hydrolysis rate constants.