Catalytic activity of butyrylcholinesterase in biodegradation of organic ammonium salts in vitro

: Organic ammonium salts of N-(2-benzoyloxyethyl)-alkyldimethylammonium bromide (BCHn-1) type are formed by the homological series Ar-COO(CH2)2-N+(CH3)2CnH2a + 1.Br-, whose structure contains a biodegradably labile ester bond, on the basis of which they rank among disinfectants and antiseptics of soft character. They are preferentially biotransformed hydrolytically to produce benzoic acid and substituted choline. The rapidity of enzymatic hydrolysis depends on the chemical structure (the length of the aliphatic chain on the ammonium nitrogen), it increases up to the number of 10 nitrogens of the aliphatic chain, and it rapidly decreases with further prolongation. The paper aimed to demonstrate the catalytic activity of butyrylcholinesterase on the enzymatic hydrolysis of selected organic ammonium salts in the medium of the microsomal fraction of the rat liver on the basis of inhibitory kinetic studies with physostigmine, a cholinesterase inhibitor. The product of enzymatic hydrolysis of BCHn-1, benzoic acid, was determined after extraction with chloroform from the acid medium by means of HPLC analysis with the use of the internal standard p-iodobenzoic acid at the wavelength of 228 nm. Kinetic parameters K(M) and VMAX were evaluated following Lineweaver-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 influenced by the presence of physostigmine, which was manifested by increased K(M), KI, and IC50 values in the investigated enzymatic process of selected substrates of the homological series BCHn-1, and by decreased VMAX and rate constants.