Enzyme polymorphism in Fasciola hepatica L.: esterases.

Homogenates of individual adult Fasciola hepatica, collected from bile ducts of sheep, were subjected to isoelectric focusing in polyacrylamide flat-bed gels after which zymograms were made by enzymatic and staining reactions. Seven identifiable isozymes that hydrolyzed alpha-naphthyl acetate were found. These 7 isozymes were identified by their isoelectric points as 5.10, 5.15, 5.25, 5.40, 5.55, 5.65, and 5.75. None of these isozymes was common to all F hepatica examined. Combinations of these isozymes in individual flukes revealed 7 distinct phenotypes, the frequency of which varied between local populations, i.e., populations of flukes obtained from individual sheep of different origin. In addition to these 7 isozymes, there were weak staining bands of enzyme activity, between pH 5.8 and the cathode end of the gels, which could not be accurately identified. The method of isoelectric focusing and zymogram preparation used in the present study did not reveal cholinesterase activity, even though the presence of activity in homogenates was demonstrated by polyacrylamide disc-gel electrophoresis. Strong activity of acid phosphatase between pH 5 and 6 was found, but poor resolution prevented obtaining accurate identification of isozymes. Weak activity with poor resolution of isozymes of alkaline phosphatase was observed between pH 4.4 and 5.75.