Esterases of the snails Helix pomatia and Cepaea hortensis. Variation and characterization of different molecular forms.

The esterase isoenzyme variation within two populations of Cepaea hortensis and one population of Helix pomatia was investigated. Different molecular forms of esterases were characterized by electrophoretic mobility, substrate preference, inhibitor/activator characteristics, molecular weight determined by gel filtration and ultracentrifugation, behaviour in response to different enzymes affecting enzyme structure and isoenzyme variation. In C. hortensis, 23 different molecular forms were identified and in H. pomatia, 14. The use of several different compounds to characterize the enzymatic specificity and the determination of the molecular weights render possible the individualization of the molecular forms. Ultracentrifugation and gelfiltration gave different molecular weight values for the same electrophoretic molecular form, which might be explained by the properties of the enzyme molecule and attachment to membrane structures. Several of the molecular forms appear to be lipoproteins, and data point to the possibility of non-specific esterases being aggregates of lipoproteins (subunits or different enzymes) with a possible dissociation into low molecular weight units.