[Properties of cholinesterase and carboxylesterase from locust ganglia].
The activity of locust ganglia cholinesterase is found to depend on concentrations of acetylthiocholine (ATC), propionylthiocholine (PTC) and butyrylthiocholine (BTC); that of carboxylesterase--on concentration of p-nitrophenylacetate (25 degrees, pH 7,5). The activity of cholinesterase is inhibited by an excess of ATC and BTC, but is unaffected by an excess of PTC. At concentrations greater than 0.01 M PTC is hydrolyzed faster than ATC at optimal (1.10(-3) M) concentration. The cholinesterase hydrolysis of BTC proceeds slower than that of ATC and PTC. The bimolecular constants (kII) of the rate of cholinesterase and carboxylesterase interaction with structurally different organophosphorus inhibitors (OPI) were determined. It was found that methylsulfomethylates of O-alkyl-S (beta-ethylmercaptoethyl) methylthiophosphonates are stronger inhibitors of cholinesterase than carboxylesterase; on the contrast, their uncharged analogs are stronger inhibitors of carboxylesterase, since the substitution of the sulfide sulphur for the sulphonic one strongly decreases the anticholinesterase activity and slightly increases the anticarboxylesterase activity of these OPI. O-alkyl-S (carbomethoxymethylmercaptomethyl) methylthiophosphonates inhibit carboxylesterase stronger than cholinesterase. The inhibitory activity of diisopropylthiophosphates towards cholinesterase is much lower than that of the corresponding diethylthiophosphates, while the activity of the former towards carboxylesterase is approximately the same as the activity of diethylthiophosphates or more strongly pronounced. Diisopropylfluorophosphate is a potent inhibitor of carboxylesterase. The data obtained provide evidence for differences in the structure of the active sites of cholinesterase and carboxylesterase. The carboxylesterase has no anionic sites. Moreover, the active surface of this enzyme interacting with the leaving part of OPI possesses, a site which prevents the absorption of cationic OPI and favours the interaction with the OPI containing the carboxyether group. The esterastic site of carboxylesterase is larger than that of cholinesterase and can predominantly interact with OPI having a bulky phosphoryl part.
D000818:Animals; D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002802:Cholinesterases / Q000378:metabolism*; D005724:Ganglia / Q000201:enzymology*; D006110:Grasshoppers / Q000201:enzymology*; D007531:Isoflurophate / Q000494:pharmacology; D007700:Kinetics; D011485:Protein Binding; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D007531:Isoflurophate; D002265:Carboxylic Ester Hydrolases; D002802:Cholinesterases
Svoĭstva kholinesterazy i karboksilesterazy gangliev saranchi.