[Catalytic activity of butyrylcholinesterase in biodegradation of organic ammonium salts in vitro]. / Katalytická aktivita butyrylcholínesterázy v biodegradácii organických amóniových solí 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.

[Inter-organ variability in enzymatic hydrolysis of ammonium salts in rats in vitro]. / Medziorgánová variabilita enzýmovej hydrolýzy organických amóniových solí u potkana in vitro.

The study evaluated the rate and kinetics of enzymatic hydrolysis of N-(2-benzoyloxyethyl)-alkyl-dimethylammonium bromides, potential easily biodegradable disinfectants of soft character. The products of enzymatic hydrolysis of the substrates under study, catalysed by microsomal esterase, included substituted substrates choline and benzoic acid which, as a hydrolytic product, was essayed by HPLC. The effect of the length of the alkyl chain of the individual homologues on the rate of enzymatic hydrolysis and their affinity to microsomal esterase of the rat liver and lung in vitro was examined. The structural modification (varying length of the aliphatic chain on the ammonium nitrogen of these compounds) was found to significantly influence the kinetics of enzymatic hydrolysis of the esteric bond. From the viewpoint of the rate of enzymatic hydrolysis no significant inter-organ variability was observed: in the liver as well as the lung the dependence of the rate of enzymatic hydrolysis on the length of the aliphatic chain possesses the shape of a falling hyperbole with the maxima for BCH2 > BCH4 > BCH8 = BCH10. The specific activity of both esterases ranges within 0.2-3.5 nmol.min-1.mg-1. From the viewpoint of affinity, a marked inter-organ difference was manifested by 10 times higher affinity of the substrates to the lung microsomal esterase in comparison with the liver one. The effect of the length of the alkyl of the individual homologues on the affinity is of a non-linear character also in this case. In both organs, a certain correlation was found between the rate of enzymatic hydrolysis and affinity to microsomal esterases.

[Metabolic N- and S-oxygenation of dokloxytepin in vitro]. / Metabolická N- a S-oxygenace dokloxytepinu in vitro.

Dokloxytepin in the medium of the induced monooxygenase system of the microsomal fraction of the liver of the rat, rabbit and mice is metabolized into three metabolites: two identical, i.e., N-oxide and 5-sulfoxide, and a third different one. In the rat and rabbit it is the hitherto unknown metabolite M1, and in the mouse S,N-dioxide of dokloxytepin. The metabolites were identified by thin-layer chromatography by comparing with synthetic standards.

[The effect of cofactors on microsomal S-oxygenation of oxyprothepine]. / Vplyv kofaktorov na mikrozomálnu S-oxygenáciu oxyprotepínu.

Oxyprothepine in the medium of the microsomal fraction of the rat liver is biotransformed to the corresponding metabolites originating by oxidation of both sulfur atoms. The formation of S-oxygenation products is bound to the presence of NADPH, with a marked synergism with NADH. Induction with phenobarbital increases the formation of the individual metabolites.