Catalytic Activity of Butyrylcholinesterase in Biodegradation of Organic AmmoniumSalts in vitro

Overview

Organicammoniumsalts of N-(2-benzoyloxyethyl)-alkyldimethylammonium bromide (BCHn-1) typeare formed by the homological seriesAr-COO(CH2)2-N+(CH3)2CnH2a+1·Br-,whose structure containsa biodegradably labile ester bond, on the basis of which they rank among disinfectants andantiseptics of soft character. They are preferentially biotransformed hydrolytically to producebenzoic acid and substituted choline. The rapidity of enzymatic hydrolysis depends on the chemicalstructure (the length of the aliphatic chain on theammoniumnitrogen), it increases up to thenumberof 10 nitrogens of the aliphatic chain, and it rapidly decreases with further prolongation. The paperaimed to demonstrate the catalytic activity of butyrylcholinesterase on the enzymatic hydrolysis ofselected organic ammonium salts in the medium of the microsomal fraction of the rat liver on thebasis of inhibitory kinetic studies with physostigmine, a cholinesterase inhibitor. The product ofenzymatic hydrolysis of BCHn-1, benzoic acid,was determined after extraction with chloroform fromthe acid medium by means of HPLC analysis with the use of the internal standard p-iodobenzoicacid at the wavelength of 228 nm. Kinetic parameters KM and VMAX were evaluated followingLineweaver-Burke using the method of linear regression analysis. The specific activity of butyrylcholinesterase(E.C.3.1.1.8) in the enzymatic hydrolytic process of BCHn-1 was significantly influencedby the presence of physostigmine, which was manifested by increased KM, KI, and IC50 valuesin the investigated enzymatic process of selected substrates of the homological series BCHn-1, andby decreased VMAX and rate constants.

Key words:
organic ammonium salts – enzymatic hydrolysis – butyrylcholinesterase –physostigmine