Structural features of carbohydrate moieties in snake venom glycoproteins

The structures of the carbohydrate moieties of glycoproteins in snake venoms are largely unknown. In the present study, we have analyzed venoms of several species of snakes as well as plasma and tissue glycoproteins from one species of cobra (Naja naja kaouthia) by lectin affinity staining of Western blots. The data demonstrate that glycoproteins in cobra venom invariably contain terminal alpha-galactosyl residues with negligible proportions of sialic acids. Interestingly, however, terminal alpha-galactosyl residues are present in significantly lower proportions in cobra tissues such as brain, liver, lung, kidney, spleen, muscle, and totally absent in cobra plasma glycoproteins. In sharp contrast to cobras, venom glycoproteins of other snakes do not contain terminal alpha-galactosyl residues but do contain terminal 2,3- and/or 2,6-linked sialic acids as well as beta-galactosyl residues. Cobra venom also contains high molecular weight heavily glycosylated proteins bearing poly-N-acetyllactosaminyl oligosaccharides, the majority of which appear to be linked to the protein core via O-glycosidic bonds.