[Mechanism of the "acetylene effect" during interaction of organophosphorus compounds with cholinesterases]. / O mekhanizme "atsetilenovogo éffecta" pri vzaimodeistvii fosfororganicheskikh soedinenii s kholinésterazami.

Here we present data on the anticholinesterase activity of 58 synthesized ethers of phosphorus thioacids with an acetylene bond in the thioether group. Anticholinesterase activity of the compounds, with acetylene group in beta and especially alpha position, in the thioether radical is many times that of their saturated analogs. Reaction between the enzymes and acetylene organophosphorous inhibitors, as well as their saturated analogs, results in phosphorylated enzyme. The triple bond plays a significant role in the acceleration of cholinesterases phosphorylation. Antienzyme activity of acetylene organophosphorous inhibitors is discussed.

[A comparative study of the cholinesterase and carboxylesterase sensitivities of mammals and arthropods to new phenyl and glycidyl esters of dialkyl thiophosphoric acid]. / Sravnitel'noe issledovanie chuvstvitel'nosti kholinesteraz i karboksilésteraz nekotorykh mlekopitaiushchikh i chlenistonogikh k novym fenilovym i glitsidilovym éfiram dialkiltiofosfornoi kisloty.

The antienzymic activities of 14 organophosphorous compounds, the derivatives of dialkyl thiophosphoric acid, towards the acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and carboxylesterase (CE) from the spring grain aphid and mammals were investigated. The dependence of inhibitory activity of the compounds on their alkyl radical length was shown to be different for the AchE from the aphid and man. Some less pronounced differences in this dependence were revealed between the BuChEs from the aphid and horse as well as between the CEs from the aphid, mouse and red spider mite. The data give evidence of a distinction in structure of the active surfaces of the enzymes from the aphid and mammals. Some peculiar properties of the aphid cholinesterases are discussed taking account of the results of the present and previous papers.

[Features of inhibiting butyrylcholinesterase and carboxylesterase hydrolysis with fluoranhydride esters of beta,beta-diphenylethylphosphonic acid]. / Osobennosti ingibirovaniia butirilkholinésteraznogo i karboksilésteraznogo gidroliza éfirami ftorangidrida beta,beta-difenilétilfosfonovoi kisloty.

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.

[Estimation of anticholinesterase activity in reversible inhibitors of cholinesterase hydrolysis]. / Ob otsenke antikholinésteraznoi aktivnosti obratimykh ingibitorov kholinésteraznogo gidroliza.

The kinetic analysis of cholinesterase interaction with reversible inhibitors was carried out. It has shown that the existing methods for definition of the type of reversible inhibition of enzyme reactions are not reliable. For example, mixed inhibition with the correlation between the competitive inhibition constant (Kl) and noncompetitive inhibition constant (K'i) less than 0.04, is identified as competitive inhibition. Apparently the ideal competitive inhibition with Ki/Ki = 0 does not exist in reality, because it is unlikely for a reversible inhibitor to decrease the process of the substrate sorption on a catalytical centre of cholinesterase not affecting the deacetylation rate. For objective evaluation of efficiency of reversible inhibitors it is suggested to determine the generalized inhibitory constant Ki at the cholinesterase hydrolysis in acetylcholine or acetylthiocholine. The data about anticholinesterase activity of carbonic and sulfoesters of lupinin are adduced.

[The mechanism of anticholinesterase action of acetylene organophosphorus inhibitors]. / O mekhanizme antikholinésteraznogo deistviia atsetilenovykh fosforororganicheskikh ingibitorov.

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.

[Influence of the substrate nature, ethanol and phosphate buffer on the butyrylcholinesterase hydrolysis retardation by reversible inhibitors]. / Vliianie prirody substrata, étanola i fosfatnogo bufera na tormozhenie butirilkholinésteraznogo gidroliza obratimymi ingibitorami.

The reversible inhibition of horse blood serum butyrylcholinesterase (Ce 3.1.1.8) hydrolysis of ion substrates of acetyl- and butyrylthiocholines and non-ion substrate of indophenylacetate by N-methyl-4-piperidinylbenzylate and tacrine (1,2,3,4,-tetrahydro-9-aminoacridine) and phosphate buffer and ethanol influence on this process are investigated. The values of competitive Ki, uncompetitive K'i and generalized K sigma inhibitory constants are determined. It is shown that the inhibition effect and reversible inhibition type depend not only on the inhibitor and substrate nature but also on the phosphate buffer concentration and ethanol presence in the reaction mixture.

[Determination of the enzyme activity in tissue homogenates and biological liquids]. / Opredelenie fermentativnoi aktivnosti v gomogenatakh tkanei i biologicheskikh zhidkostiakh.

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.

[Anticholinesterase activity of alkyl esters of perfluoroalkyl phosphonic and perfluoroalkyl phosphinic acids]. / Antikholinésteraznaia aktivnost' alkil'nykh éfirov perftoralkilfosfonovoi i perftoralkilfosfinovoi kislot.

It has been demonstrated that esters (RO)2P(O)X and RO(R1)P(O)X where R and R1-alkyls, X-CF3 or C2F5, irreversibly inhibited cholinesterases. Their inhibitory effect increased with the elongation of alkyl radicals from CH3- to C4H9-, being more evident with respect to butyrylcholinesterase from horse serum than to acetylcholinesterase from human erythrocytes. It is shown that the concept on inability of esters of thiophosphoric acids to inhibit cholinesterases due to the fact that thionic sulphur (P-S) does not form a strong hydrogen bonds, cannot be applied to esters of perfluorothiophosphonic acids: (C2H5O)2P(S)CF3 inhibits cholinesterases more efficiently than (C2H5O)2P(O)CF3. One of the fluoric atoms probably forms hydrogen bond with the corresponding site of the active centre in cholinesterases, similar to phosphorylic oxygen (P-O) in case of the enzyme inhibition by esters of phosphoric acids.

[Reversible inhibition of cholinesterases by salts of pyrilium, thiopyrilium and selenopyrilium derivatives]. / Obratimoe ingibirovanie kholinésteraz soliami proizvodnykh piriliia, tiopiriliia i selenopiriliia.

Salts of pyrilium, thiopyrilium and selenopyrilium derivatives at pH 7.5 and temperature of 25 degrees C are studied for their effect on the catalytic activity of acetyl cholinesterase (EC 3.1.1.7) of human blood erythrocytes and butyryl cholinesterase (EC 3.1.1.8) of horse blood serum which is measured by the method of potentiometric titration. All enumerated salts are established to be strong reversible inhibitors of mixed-type cholinesterases, that is testified by small values of the inhibitory constants: competitive Ki, noncompetitive K'i and generalized K epsilon. Pyrilium and selenopyrilium salts inhibit acetyl cholinesterase of human blood erythrocytes to a higher extent than butyryl cholinesterase of horse blood serum, and thiopyrilium salts inhibit the latter to the highest extent. By the value of the inhibitory effect on acetyl cholinesterase of human blood erythrocytes thiopyrilium salts exceed the analogous pyrilium salts, whereas in experiments with butyl cholinesterase of horse blood serum there is an opposite dependence.

[A method of determining inhibitory constants during reversible inhibition of enzymatic hydrolysis of a substrate]. / Metod opredeleniia ingibitornykh konstant pri obratimom tormozhenii fermentativnogo gidroliza substrata.

Determination of inhibitory constants and antienzymic activity of reversible retardants of different type of action by the generalized inhibitory constant K sigma is estimated, results being presented. To determine more precisely the values of inhibitory constants of the competitive (Ki), noncompetitive (K'i) inhibition and of the generalized K sigma it is suggested to conduct linearization of the experimental data in coordinates: 1/K sigma, s; 1/[S], where K sigma, s is a total inhibitory constant whose value depends on the substrate [S] concentration and to make calculations by the least-square method with the allowance for principal intervals of the Km values and the maximal rate of the enzymic reaction V. Comparative calculations are made by a computer using the BASIC/RT-60 language programme through the example of the acetyl choline acetyl hydrolase (EC 3.1.1.7) interaction with the quaternary phosphonium salts--reversible retardants of this enzyme.

[Comparative sensitivity of 2 carboxylesterases from the reindeer liver to various inhibitors]. / Sravnitel'naia chuvstvitel'nost' dvukh karboksilésteraz iz pecheni severnogo olenia k nekotorym ingibitoram.

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.

[Inhibition of cholinesterases by quaternary phosphonium compounds]. / Ingibirovanie kholinésteraz chetvertichnymi fosfonievymi soedineniiami.

Alkyl tributylphosphonium and triphenylphosphonium derivatives as well as tetraphenylphosphonium were first studied as inhibitors of acetylcholinesterase of human blood erythrocytes and butyrylcholinesterase of horse blood serum. The inhibition is reversible, of mixed type, with a different contribution of competitive and uncompetitive components. The value of the inhibitory effect is essentially dependent on the structure of phosphonium compounds, especially in experiments with butyrylcholinesterase: allyltriphenylphosphonium is 290 times as strong enzyme inhibitor as methyltributylphosphonium. Hexyltributylphosphonium is identical to hexyltributylammonium in both the pattern and efficiency of the inhibitory action on cholinesterases.

[Reversible inhibition of acetylcholinesterases of different origins by quaternary phosphonium compounds]. / Obratimoe tormozhenie atsetilkholinésteraz razlichnogo proiskhozhdeniia chetvertichnymi fosfonievymi soedineniiami.

Studies have been made on the reversible inhibition of acetylcholinesterase activity from the erythrocytes of man, horse and camel, the electric organ of the skate Torpedo marmorata and eel Electrophorus electricus, the venom of the snakes Naja naja and Vipera lebetina, the brain of the pigeon Columba livia by tetraphenyl-, triphenylalkyl- and tributyrylalkyl-phosphonium salts. The investigated phosphonium inhibitors exhibit an evident specificity in their action: they were more effective in inhibiting the acetylcholinesterase from human erythrocytes than that from the erythrocytes of horse and camel. These salts were more effective with respect to the acetylcholinesterase activity of the electric organ of the skate than that of the electric organ of the eel. Acetylcholinesterases from the venom of the snakes exhibited practically identical sensitivity to all the phosphonium compounds investigated. The present work is the first attempt to use quaternary phosphonium salts (the so-called "hydrophobic ions") in comparative enzymological investigation.

[Interaction between various cholinesterases and reversible inhibitors of polymethylene-bis-(trimethylammonium) diiodide series]. / Vzaimodeistvie razlichnykh kholinésteraz s obratimymi ingibitorami riada polimetilenbis(trimetilammonii)diiodidov.

It is established that derivatives of polymethylene bistrimethylammonium (CH3)3N+(CH2)nN+(CH3)3 (n = 4-10) are reversible competitive and mixed action inhibitors with respect to acetylcholinesterase of human erythrocytes, butyryl cholinesterase of horse blood serum, cholinesterase of frog brain and Todarodes pacificus optical ganglion. In case of mammals and frog cholinesterase the inhibitors efficiency rises with n, but the activity of the Todarodes pacificus cholinesterase less sensitive of the inhibitors is characterized by a "step" dependence on the length of the polymethylene chain of the inhibitor molecule. Studies in sensitivity of cholinesterases to this type of inhibitors revealed differences between enzymes of the same type in different animals.

[Effect of substituted thiobutinylic esters of phosphorus thio acids and their saturated analogs on cholinesterases of different origins]. / Deistvie nekotorykh zameshchennykh tiobutinilovykh éfirov tiokislot fosfora i ikh nasyshchennykh analogov na kholinésterazy razlichnogo proiskhozhdeniia.

Studies have been made of the effect of organophosphorus inhibitors (OPI) containing butynilic group in the detectable part of the molecule, and of their saturated analogues on cholinesterases from different species of mammals and arthropods. In all cases without a single exception, acetylene compounds exhibited higher anticholinesterase effect than saturated ones. The value of "acetylene effect" varied to a great extent and depended on both the structure of OPI and the source of cholinesterase, these data indicating the existence of differences in the structure of the active site in cholinesterases investigated. The acetylene effect was always higher in ethylmercapto-substituted OPI than in chloride-substituted ones. Among thiophosphates, the highest (7,600) effect was found for cholinesterase of the spider mite in the case of dimethyl esters. Among thiophosphonates, exceptionally high (38,000) effect was noted for cholinesterase from the head of the domestic fly when methylthiophosphonates were compared. In this pair of compounds, the inhibitory constant k2 for the cholinesterase of the fly by acetylene derivative was equal to 1.1 . 10(9).