[Mechanism of the "acetylene effect" during interaction of organophosphorus compounds with cholinesterases].

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.

[Biochemical characteristics of aminostigmine--a new anticholinesterase agent].

The properties of aminostigmine in comparison with those of other carbamate inhibitors of cholinesterases have been studied in vitro using potentiometric titration and Ellman methods. The bimolecular constants of the inhibition rate of acetyl-, butyryl- and propionylcholinesterase were found to be equal to (8.0-14.

[A comparative study of carboxylesterase in the white mouse and in the caterpillar of the cotton bollworm Heliothes armigera].

Studies have been made on enzymic hydrolysis of p-nitrophenylacetate (p-NPhAc), n-nitrophenylbutyrate (p-NPhBu) and indophenylacetate (IPhAc) by carboxylesterase (CE) from mouse blood plasma and liver as well as from caterpillar of the cotton worm haemolymph, intestine and fat body. Different KM and V max values were obtained for CE from these sources. The highest specific activity of CE from mouse liver and caterpillar intestine and fat body was observed with p-NPhBu.

[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.

[The effect of pH and reversible inhibitors on decarbamylation of acetylcholinesterase].

Decarbamylation rate of membrane-bound methyl- and dimethyl-carbamylated acetylcholinesterase of human erythrocytes and bovine brain is reliably 1.1-1.6 times lower than that of the soluble enzyme.