Inhibition of acetylcholinesterase hydrolysis of cationic substrates by the reaction product

The kinetics of acetylcholinesterase-catalyzed hydrolysis of the two cationic substrates (I and II in Russian text) was analyzed by means of the integrated Michaelis equation (3). The constants kII, kcat Km and the enzyme-product complex dissociation constant Ki were determined. (Table 1). It was shown that acetylcholine (II) binds to to the enzyme active center more effectively than the alcohol product of its hydrolysis. In case of the pipecholine derivative (I) reversed situation occurs. The different dependence of the ester substrate and appropriate alcohol binding effectiveness upon the reagent structure indicates the dissimilar location of the molecules in the active center of acetylcholinesterase. Some structural implications of the enzyme active center were discussed.     

Study of cholinesterases of different origin by the method of inhibitor analysis (variation of structure of phosphoryl and leaving parts of dialkoxyphosphates)

Analytical review is performed of literature data on inhibitor analysis of structure of cholinesterases from different animals (vertebrates, insects, molluscs) by studying rate of their interaction with 190 dialkoxyphosphates of 54 homologous series with regularly changed structure of their phosphoryl group. The presented data are discussed from the point of view of comparative biochemistry and in the light of current concepts of structure of cholinesterase active center in animals at different levels of evolutionary development.     

Comparative-enzymological study of cholinesterases from optic ganglia of the Commander squid Berryteuthis magister individuals inhabiting different zones of the species area

In this review a comparative analysis is performed of enzymological characteristics of cholinesterase (ChE) from optic ganglia of individuals of the Commander squid Berryteuthis magister caught in 8 zones of its habitation area in the northern-western Pacific aquatorium, of ChE of the Pacific squid Todarodes pacificus as well as of the “standard” acetylcholinesterase from human erythrocytes and butyrylcholinesterase from horse blood serum. By the method of the substrate-inhibitor analysis there was shown homogeneity of ChE preparations from the B. magister individuals from different habitation zones. Kinetic parameters of the enzymatic hydrolysis of 8 ester substrates are presented as well as the data on study of identity of ChE properties in the B. magister individuals from different habitation zones. Study of the process of the ChE reversible inhibition from the Commander squid individuals under action of 57 mono- and bisonium inhibitors has revealed differences in ChE properties in squid individuals from isolates in different zones of the habitation area, which argues in favor of the existence of intraspecies groups of the Commander squid B. magister.     

Larvae of related Diptera species from thermally contrasting habitats exhibit continuous up-regulation of heat shock proteins and high thermotolerance

A population of Stratiomys japonica, a species belonging to the family Stratiomyidae (Diptera), common name ‘soldier flies’, occurs in a hot volcanic spring, which is apparently among the most inhospitable environments for animals because of chemical and thermal conditions. Larvae of this species, which naturally often experience temperatures more than 40 °C, have constitutively high concentrations of the normally inducible heat-shock protein Hsp70, but very low level of corresponding mRNA. Larvae of three other species of the same family, Stratiomys singularior, Nemotelus bipunctatus and Oxycera pardalina, are confined to different type semi-aquatic habitats with contrasting thermal regime. However, all of them shared the same pattern of Hsp70 expression. Interestingly, heat-shock treatment of S. japonica larvae activates heat-shock factor and significantly induces Hsp70 synthesis, whereas larvae of O. pardalina, a species from constant cold environment, produce significantly less Hsp70 in response to heat shock. Adults of the four species also exhibit lower, but detectable levels of Hsp70 without heat shock. Larvae of all species studied have very high tolerance to temperature stress in comparison with other Diptera species investigated, probably representing an inherent adaptive feature of all Stratiomyidae enabling successful colonization of highly variable and extreme habitats.     

How aliphatic alcohols and pH affect reactivity of horse blood serum cholinesterase at its interaction with organophosphorus inhibitors

There was studied action of aliphatic alcohols (ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol), and pH on various kinds of serum cholinesterase. At inhibition of the cholinesterase hydrolytic activity under effect of alcohols the key role was played not by the total number of carbon atoms in the alcohol molecule, but by the “efficient length” of the carbohydrate chain. The fact that the presence of alcohols did not affect parameters of reversible inhibition of cholinesterase by onium ions tetramethylammonium and choline allows suggesting the absence of action of solvents on specific sorption of acetylcholine in the enzyme active center. With aid of two sets of hydrophobic organophosphorus inhibitors (OPI) (12 compounds), we have managed to estimate both the degree and the character itself of serum cholinesterase.     

Quaternary phosphonium reversibile inhibitors of cholinesterases of different animals

Quaternary phosphonium compounds were found to be reversible inhibitors of cholinesterases of various animals and showed species-specificity of action depending on the inhibitor structure. It became possible to reveal difference in inhibitory specificity of various preparations of acetylcholinesterases. A difference has been shown in inhibitory parameters of the series of phosphonium toward cholinesterase of visual ganglia of individuals of the squid Berryteuthis magister from different zones of the habitat areal. For the first time, when comparing phosphonium and ammonium isologues - tetrabutyl- and tributylhe-xyl derivatives, it has been shown that they are agents practically similar by the character of anticholinesterase action.