Echinococcus granulosus: specificity of amino acid transport systems in protoscoleces

Abstract

Protoscoleces of Echinococcus granulosus absorb the L-amino acids proline, methionine, leucine, alanine, serine, phenylalanine, lysine and glutamic acid by a combination of mediated transport and diffusion. All eight amino acids were accumulated against a concentration gradient. Comparison of Kt and Vmax values suggests that a low affinity for a particular compound is compensated for by a relatively larger number of transport sites for that compound. Four systems serve for the transport of the eight substrates studied: 2 for neutral (EgN1, EgN2) and 1 each for acidic (EgA) and basic (EgB) amino acids. All eight amino acids are incorporated into protein to varying degrees and substantial portions of absorbed L-alanine and L-methionine are metabolized into other compounds.

Echinococcus granulosus: a comparison of free amino acid concentration in hydatid fluid from primary and secondary cysts and host plasma

“…FAAs can enter or leave the pool through the germinal membrane/laminated layer on the host side and, in the case of fertile cysts, to or from the protoscoleces via the brood capsule wall on the inside. Jeffs & Arme (1987) have demonstrated that, in vitro, equine protoscoleces can absorb several amino acids by a combination of diffusion and mediated transport. Data obtained from an examination of the uptake of four amino acids by Sem cysts indicated that, here too, receptor-mediated transport occurred (Jeffs & Arme, 1988).…”

“…The FAAs in hydatid fluid can be regarded as an intracellular pool composed of a component derived from uptake from surrounding host tissue and a catabolic component, (see above) resulting from protein degradation and other metabolic transformations occurring within the parasite tissues (see Frayha & Haddad (1980), Harris (1983) and Jeffs & Arme (1987) for the few data on amino acid metabolism available).…”

“…In our laboratory attention has recently been focused upon the characterization, in vitro, of amino acid and glucose transport sites of protoscoleces of equine Echinococcus granulosus and secondary equine hydatid cysts grown in mice (Jeffs & Arme, 1987, 1988. This work has generated an interest in the precise composition of hydatid fluid in vivo, forming as it does a bathing fluid surrounding brood capsules and the inner germinal membrane of the cyst.…”

Spatiotemporal Expression Patterns and Antibody Reactivity of Taeniidae Endophilin B1

“…Most platyhelminths utilize endocytosis to take up nutrients and other essential resources from the host environments, due to their limited capacity for metabolism (32,33). In addition, the tegument plays multifunctional roles in osmoregulation and excretion of waste products (34).…”

Sequencing, bioinformatic characterization and expression pattern of a putative amino acid transporter from the parasitic cestode Echinococcus granulosus

“…As a consequence of a parasitic way of life, the amino acid metabolism is very limited and the adult worm must fulfill most of its amino acid requirements by active tegumental absorption from the intestinal amino acid pool (Wack et al, 1983). It was shown that E. granulosus protoscoleces are able to accumulate L-amino acids and it was suggested the existence of various systems for the absorption of amino acids (Jeffs and Arme, 1987;Allen and Arme, 1991). Also, it was found that amino acids in the hydatid cyst fluid were severalfold more concentrated than in host plasma (Jeffs and Arme, 1988;Hurd, 1989;Çelik et al, 2001) suggesting that the cyst wall is not freely permeable to metabolites.…”