Assay for sialidase using erythrocytes and peroxidase-labeled peanut lectin

A rapid and sensitive sialidase assay method based on peroxidase-labeled peanut lectin (PNA) binding to desialylated erythrocyte is described. Formalinized sheep erythrocytes were used both as a stable substrate for sialidase and as a target for the lectin. In the case of sialidases from Vibrio cholerae and Arthrobacter ureafaciens, a linear relationship was observed between the amount of peroxidase-labeled PNA bound to erythrocytes and the enzyme amount. Binding of the lectin to sialidase-treated erythrocytes was completely prevented in the presence of 25 mM lactose and galactose. The method is particularly useful as a selective assay for sialidase which is active towards gangliosides or sialoglycoproteins, because a mammalian sialidase which is preferentially active towards sialooligosaccharides and sialoglycopeptides is not able to remove sialic acid from erythrocytes.