[Selectivity of the effect on cholinesterase of stereoisomers of thiophosphonates with asymmetrical phosphorus atoms].
The inhibitory action of stereoisomers of organophosphorous compounds with asymmetric phosphorous atom, (CH3)2CHO(CH3)P(O)SCH2CH2SC2H5 and (CH3)2CHO(CH3). .P(O)(CH2)3CH3, on acetylcholinesterase from nervous ganglia of cockroach Periplaneta americana and bovine erythrocytes as well as on horse serum butyrylcholinesterase was studied at pH 7.5 and 25 degrees C. It was found that the interaction of the inhibitors with cholinesterases has a complex type and includes reversible and irreversible stages resulting in the formation of noncovalent enzyme-inhibitor complex and phosphorylation of the enzyme, respectively. The affinity constants Ka, phosphorylation rate-constants kp, bimolecular reaction constants kII for enzyme inhibition, as well as the dissociation constants Ki, r for unproductive sorbtion of inhibitor were determined. Much greater selectivity in the action of (-)isomers of both thiophosphonates, as compared to (+)isomers, on acetylcholinesterases were observed, the effect being most pronounced for the cockroach enzyme. On the other hand, no marked differences were discerned between isomers in their binding to butyrylcholinesterase. The stereospecificity of the enzymes under study at different stages of interaction with the inhibitors was characterized.
D002800:Cholinesterase Inhibitors; D066298:In Vitro Techniques; D007700:Kinetics; D009946:Organothiophosphorus Compounds / Q000494:pharmacology*; D013237:Stereoisomerism
D002800:Cholinesterase Inhibitors; D009946:Organothiophosphorus Compounds
Izbiratel'nost' deĭstviia na kholinésterazy stereoizomerov tiofosfonatov s asimmetricheskim atomom fosfora.