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Two novel lectins that bind selectively to trematode-associated fucosylated determinants have been characterized and purified from the hemolymph of wild-type rock-dwelling Turbo coronatus and mud-dwelling Cerithidea cingulata snails inhabiting Kuwait Bay. Both lectins were separately purified from the hemolymph of T. coronatus (designated Tc lectin) and C. cingulata (designated Cc lectin) by affinity chromatography on immobilized L-fucose-agarose columns and elution with a gradient of 0.1-1 M L-fucose. Assessments of the structural characteristics, by one- and two-dimensional polyacrylamide gel electrophoresis, indicated that Tc and Cc lectins were structurally distinct, and exist in their native forms as multimers of non-covalently associated subunits of different sizes and pIs. Removal of N-linked glycans by endo-beta-N-acetylglucosaminidase F resolved the heterodisperse pattern of Tc lectin subunits into 31 and 27 kDa components (each with a pI of 7.8) as well as an 8 kDa component with a pI of 7.2, and collapsed the size microheterogeneity of the Cc lectin subunits into a single spot of 33 kDa (pI 5.4). Each of these subunits is subjected to differential post-translational N-linked glycosylations, which involve variable acidic complex-type units in Tc lectin and neutral high-mannose-type units in Cc lectin. Based on trematode glycoprotein binding and inhibition assays, the two lectins exhibited optimum binding at a similar pH range, but were distinct in terms of their temperature stability as well as binding affinities towards the fucose moiety constituting the fucosylated target.

Lipids of the digestive gland of the mollusc Littorina saxatilis from the White and Barents Seas were studied. Changes of its biochemical composition are discussed in the connection with different temperature of the habitat and with infestation with trematode larvae. Comparative analysis of the fatty acid (FA) composition of each of phospholipids in intact molluscs has revealed essential differences. Phosphatidylcholine and monophosphatidylinositol (MPI) FA did not differ in the omega 3/omega 6 ratio, which is due to their tolerance to the temperature factor, whereas more unsaturated phospholipids--phosphatidylethanolamine (FEA), its plasmalogen form (pFEA), and phosphatidylserine--differed 1.5-2 times in the studied molluscs. Predominance of omega 3 acids in the Borents Sea molluscs undoubtedly is due to the lower habitat temperatures, as it provides a higher fluidity of membrane phospholipids. Infestation affected to the greatest degree the quantitative FA composition in pFEA and MPI. At infestation, out of all considered phospholipids, only in MPI there was revealed a threefold decrease of the content of eikosenoic acid C20 : 1, whereas in all other phospholipids, in the contrary, it increased. Monophosphatidylinositols also differed essentially from other phospholipids by the saturated FA amount, which changed the unsaturation index of these phospholipids. Since the functional significance of this minor phospholipid is determined by its participation in the so-called phosphatidylinositol system of the hormonal signal transduction, it seems interesting to elucidate whether an increase of this membrane phospholipid saturation at invasion affects the reflex connection between signals from receptors located in a parasite and enzymatic processes.