The anomeric specificity of six sialidases (Vibrio cholerae, Arthrobacter ureafaciens, Clostridium perfringens, Newcastle disease virus, fowl plague virus and influenza A2 virus sialidases) was assessed with sialylated antifreeze glycoprotein, ovine submandibular gland glycoprotein and alpha 1-acid glycoprotein, resialylated specifically in alpha(2-3) or alpha(2-6) linkage with N-acetylneuraminic acid or N-glycolylneuraminic acid using highly purified sialyltransferases. The rate of release of sialic acid from these substrates was found to correlate well with the specificity observed earlier with the same sialidases using small oligosaccharide substrates, i.e., alpha(2-3) glycosidic linkages are hydrolyzed faster than alpha(2-6) linkages, with the exception of the enzyme from A. ureafaciens. Sialidase activity was higher with N-acetylneuraminic acid when compared with N-glycolylneuraminic acid. The studies also showed that the core oligosaccharide and protein structure in glycoproteins may influence the rate of release for different glycosidic linkages.