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Biomedical subjects

A P Brestkin

Publications and source records attributed to A P Brestkin.

At least 19 recordsLinked to original sources
PubMed1996

[Features of inhibiting butyrylcholinesterase and carboxylesterase hydrolysis with fluoranhydride esters of beta,beta-diphenylethylphosphonic acid].

A new type of organophosphorus compounds-beta, beta-diphenylethylphosphonic acid fluoroanhydride esters-with various alkyl radicals (CH3, C2H5, C3H7, i-C3H7, C4H9, i-C4H9, C5H11, C6H13) and a phenyl radical (C6H5) have been tested as inhibitors of horse serum butyryl cholinesterase (EC 3.1.1.8) and two forms of reindeer liver carboxyl esterase (EC 3.1.1.1). All the tested compounds are strong irreversible inhibitors of butyryl cholinesterase and strong combined type inhibitors of carboxylesterase. The values of inhibitory constants have been found to depend on the structure of the alkyl radical in the inhibitor molecule.

Anhydrides↗
PubMed1992

[The mechanism of anticholinesterase action of acetylene organophosphorus inhibitors].

Introduction of the triple bond in the leaving group of the organophosphorus inhibitor molecule gives a sharp raise of the inhibitor activity but does not change principal characteristics of the cholinesterase inhibition mechanism. The reactivation experiments suggest that inactivation of cholinesterases by these compounds occurs due to phosphorylating of the serine hydroxyl by the corresponding phosphoric acid. A close similarity was shown between acetylenic and saturated organophosphorus inhibitors in altering ka upon change of pH and tetraalkylammonium ions action. It is demonstrated that S-alkynyl esters of thioacetic acid are slowly hydrolyzed by acetylcholinesterase and cholinesterase without irreversible inhibition of the enzymes.

Acetylene↗
PubMed1989

[Determination of the enzyme activity in tissue homogenates and biological liquids].

The described method for measuring the enzymic activities in tissue homogenates and biological fluids is based on the separation of the space with the biological fluid, where the enzymic reaction takes place, from the space with the substrate solution, where the analytical effect is measured, by a semipermeable membrane. The authors present the results of measurements of monoamine oxidase activity in rat liver mitochondria homogenate, of acetylcholinesterase activity in mouse brain homogenate, and of cholinesterase activity in cow blood serum.

Animals↗
PubMed1986

[Comparative sensitivity of 2 carboxylesterases from the reindeer liver to various inhibitors].

The sensitivity to the inhibitor of two forms of reindeer liver carboxylesterases differing in electrophoretic mobility and conventionally termed as "slow" and "fast" forms were investigated. The rate constants for the interaction of organophosphorous irreversible inhibitors--diisopropylfluorophosphate (DPP) and two methylthiophosphonic acid thioesters--C5H11O(CH3)P(O)S(CH2)SCH2C(O)OCH3 (Sh-205) and, C8H17O(CH3)P(O)S(CH2)SCH2C(O)OCH2 (Sh-207)--with the "fast" form are hundreds of times as high as those with the "slow" one. The rate constants for irreversible carbamate inhibitor interaction byehone with both carboxylesterase forms were approximately equal to 1.2 X 10(3) M-1 X min-1 and 2.0 X 10(3) M-1 X min-1, respectively. The reversible inhibitors potassium benzylate and kathapin also inhibited the "fast" carboxylesterase form in the indophenylacetate (IPA) hydrolysis reaction (770 and 1700-fold, respectively). On the contrary, N-methylpiperidinyl ester of benzyl acid inhibited the "slow" form three times stronger. Carbophos reversibly inhibited IPA hydrolysis in the presence of both enzyme forms, but the carboxyester carbophos group was hydrolyzed at a measurable speed only by the "slow" form.

Animals↗
PubMed1982

[Not Available].

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History, Modern 1601-↗
PubMed1982

[Stereospecificity of active centers of acylcholinesterases].

The stereospecificity of the active center of acetylcholinesterase from human erythrocytes (AChE) and butyrylcholinesterase from horse blood serum (BuChE) in reactions with enantiomers of irreversible organophosphorus inhibitors (OPI) with asymmetrical central phosphorus atom and different structure of the leaving moiety: C2H5O(CH3)P(O)SR, where R = C2H7; C6H13: C4H4SC2H5; C2H4SC2H5 and C2H4S(CH3)C2H5, was studied. The strongest inhibiting effect with respect to cholinesterases was exerted by (-)-isomers of the OPI tested. The differences in the inhibiting activity of (-) and (+)-isomers were especially well-pronounced for OPI with R = C3H7 and C4H4SC2H5. The differences in the inhibiting activity of the enantiomers suggest that the stereospecificity of the active center of AChE was the highest and that of BuChE was considerably lower. After treatment by N,N-dimethyl-2-phenylaziridinium ions which specifically and irreversibly modify the anionic groups on the active surface of AChE, the stereospecificity of the latter is decreased and is approximated to that of BuChE. The differences in stereospecificity of AChE and BuChE are probably due to the considerable differences in the spatial structure of the enzyme active centers.

Acetylcholinesterase↗
PubMed1981

[Interaction of frog brain cholinesterase with some reversible ammonium inhibitors].

The effects of some ammonium compounds diiodomethylate acetate (I), propionate (II), butyrate (III), valeriate (IV) N-hydroxyethylanabasine, tetramethylammonium, tetraethylammonium and acetylcholine amide analog derivatives (V-VIII) on acetylthiocholine hydrolysis by cholinesterase from frog brain, acetylcholinesterase from human erythrocytes and butyryl cholinesterase from horse blood serum were studied. Cholinesterase from frog brain possesses a lower sensitivity to the inhibitors than does the mammalian enzyme. Significant conformational changes of the inhibitor molecule, i. e. transition from trans-conformation (V) to the fixed gosh-conformation (VII), have no effect on the anticholinesterase activity of these compounds. A method for evaluation of effectivity of different types of the reversible inhibitors is proposed.

Animals↗