A comparison of the cholinesterases of an oyster (Crassostrea virginica) and a clam (Macrocallista nimbosa)
- 1 November 1976
- journal article
- research article
- Published by Wiley in Journal of Experimental Zoology
- Vol. 198 (2), 121-134
- https://doi.org/10.1002/jez.1401980202
Abstract
Cholinesterase activities in the hearts and ganglia of an oyster (Crassostrea virginica) and a venerid clam (Macrocallista nimbosa) were measured and compared. Tissue extracts were partially purified by ammonium sulfate fractionation followed by gel column chromatography. Enzymatic activity was assayed spectrophotometrically; substrates were acetyl‐, butyryl‐, and propionylthiocholine (ATC, BTC, PTC). Kinetic constants characterizing each enzyme were derived. At all substrate concentrations, the hydrolysis rates of both clam enzymes were in the order: BTC > PTC > ATC. With oyster enzymes the ranking was ATC ≥ PTC > BTC. The specific activities of oyster heart and ganglion enzymes were similar. In contrast, clam ganglion extracts were 75–100 times more active than clam heart extracts and, with any substrate, had greater activity than either oyster enzyme. All enzyme preparations proved to be homogeneous on the bases of constant substrate activity ratios in successive column fractions, and of intermediate velocities with mixed substrates. Six cholinesterase inhibitors were tested. The specific acetylcholinesterase antagonist, B.W. 62c47, was much more effective against oyster enzymes, while the specific antibutylcholinesterase, iso‐OMPA, almost totally inhibited clam enzyme activity, but had little effect on oyster. Eserine was the most effective inhibitor of both enzymes. In conclusion, the enzymes in oyster tissues are acetylcholinesterases, while clam enzymes are butyrylcholinesterases. Nevertheless, clam ganglion esterase is sifficiently active to hydrolyze the physiological substrate, acetyl‐choline. These results explain the long‐observed differences in isolated heart pharmacology between ostreid and venerid bivalves.This publication has 25 references indexed in Scilit:
- Propionylcholinesterase in the nervous ganglia of the fresh-water pulmonate mollusc Lymnaea stagnalisComparative Biochemistry and Physiology Part A: Physiology, 1973
- A comparison of acetylcholine structure—Activity relations on the hearts of bivalve molluscsComparative Biochemistry and Physiology, 1970
- Cholinesterase in boll weevils, Anthonomus grandis Boheman—I. Distribution and some properties of the crude enzymeComparative Biochemistry and Physiology, 1968
- Separation and properties of subcellular particles associated with 5-hydroxytryptamine, with acethylcholine and with an unidentified cardio-excitatory substance from Mercenaria nervous tissueComparative Biochemistry and Physiology, 1966
- A compendium of responses of bivalve hearts to acetylcholineComparative Biochemistry and Physiology, 1965
- Classification and Comparative Enzymology of the Cholinesterases and Methods for their DeterminationPublished by Springer Nature ,1963
- Structure-Activity Relationships of the Reversible Anticholinesterase AgentsPublished by Springer Nature ,1963
- A new and rapid colorimetric determination of acetylcholinesterase activityBiochemical Pharmacology, 1961
- The esterases of horse blood. 1. The specificity of horse plasma cholinesterase and ali-esteraseBiochemical Journal, 1950
- The Effect of Enterogastrone on the Gastric Secretion of the Cat Stimulated toy Continuous Administration of HistamineActa Physiologica Scandinavica, 1948