Inhibitor Analysis of Cholinesterases of Different Origin (Variation of Structure of Leaving Group of Organophosphorus Inhibitors)

There is presented an analytic review of literature data on inhibitory analysis of structure of cholinesterases of different animals (vertebrates, insects, and molluscs) performed by studying rate of their interaction with 64 organophosphorus compounds of 13 series with different structure of leaving group. The presented data are considered from the point of view of comparative biochemistry and in the light of current data on structure of the cholinesterase active center.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 3, 2005, pp. 201–216.Original Russian Text Copyright © 2005 by Moralev, Rozengart.     

Boundaries of the butyrylcholinesterase anion site from data of a conformational analysis of substrates

By means of molecular mechanics, theoretical conformational analysis has been made of 19 substrates of butyrylcholinesterase - acetylcholine derivatives with different structure of the ammonium group. It was concluded that the anionic point is located in the cavity of the enzymic molecule. Dimensions and shape of this cavity were established which provide satisfactory correlation between its filling by substrate conformers and the rate of their enzymic hydrolysis. Some suggestions were made with respect to the mechanism of the effect of non-productive sorbtion of the substrates on the rate of their enzymic hydrolysis.     

A comparative study of the effect of vinyl phosphoric acid esters on cholinesterase and carboxylesterase activities in mammals and arthropods

Studies have been made of the effect of organophosphorus inhibitors on cholinesterase and carboxylesterase from various mammals (human erythrocytes, mouse brain, blood serum of mouse and rat, blood serum of horse) and arthropods (Calliphora vicina, Schizaphis graminum, Myzus persicae, Sitophilus oryzae, Pseudococcus maritimus, Tetranychus urticae). Organophosphorus inhibitors were presented by esters of vynylphosphoric acid containing normal and branched alkyls in the phosphoryl part of the molecule. The increase of the radical up to a propyl one increased the effect of organophosphorus inhibitors with respect to cholinesterase from the majority of the arthropods investigated. Organophosphorus compound with an isopropyl radical was found to be weaker for all the enzymes studied. Extremely high sensitivity of carboxylesterase from all arthropods to all organophosphorus inhibitors was noted; in some of the cases, anticarboxylesterase activity of all drugs was 2-3 orders higher than anticholinesterase one (P. maritimus, T. urticae). Regularities established for cholinesterase practically completely were confirmed on carboxylesterase. This finding evidently reveals similar structure of catalytic surface at the vicinity of esterase center in both enzymes.     

Comparison of the cholinoreceptor and cholinesterase properties of the frog Rana temporaria and the squid Todarodes pacificus

Studies have been made on the interaction of several groups of quartenary ammonium salts with cholinoreceptors of m. rectus abdominis of the frog Rana temporaria, and isolated m. retractor infundibuli of the octopus Todarodes pacificus, as well as with cholinesterases of the frog brain and visual ganglia of the octopus. The derivatives of polymethylene bis(trimethylammonium) compounds, being cholinomimetic drugs for frog muscle, do not exert cholinomimetic influence on octopus muscle. The same difference with respect to their effect on frog and octopus receptors was found in anabazin derivatives. Among amide derivatives of acetylcholine, the strongest mimetic effect on cholinoreceptors of both animals was exhibited by a piperazine isolog with gauche-conformation, whereas N-methyl isolog with trans-conformation was found to be the strongest inhibitor of cholinesterases. Cholinoreceptors and cholinesterase of the octopus were less sensitive to the effect of the investigated quartenary ammonium salts than those of the frog.     

Interaction between various cholinesterases and reversible inhibitors of polymethylene-bis-(trimethylammonium) diiodide series

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.