Leucine aminopeptidase activity in adults of Pomphorhynchus laevis (Acanthocephala): a histochemical study

In frozen sections of the acanthocephalan Pomphorhynchus laevis, which is a frequent intestinal parasite of cyprinid and salmonid fishes, leucine aminopeptidase (APase) was localized histochemically in outer parts of the presomal bulbus as well as in all layers and most nuclei of the metasomal body wall. Enzyme activity visualized at pH 6.5 using L-leucyl-4-methoxy-2-naphtylamide as the substrate was also associated with ovarian balls, immature larvae, and the testes. The results are discussed with respect to the possible function of APases and the proposed sites of amino acid uptake in tissues of P. laevis.