The Specificity of Sialyltransferases Using Glycosylated Lysozyme Derivatives as Substrates

Abstract

Galactose, lactose, N-acetylgalactosamine, N-acetylglucosamine and fibrinoglycopeptides were bound to lysozyme by different linkages. These glycosylated lysozymes were tested as N-acetylneuraminic acid acceptors using particular sialyltransferase preparations from frog and bovine liver and from bovine and porcine submandibular glands. Desialylated fetuin served as the reference compound. Galactose residues of desialo-fetuin and lysozyme-lactose are sialylated by all 4 sialyltransferases tested, galactose bound to lysozyme via a phenylazo group is inactive with the enzyme from bovine submandibular gland, and galactose bound directly to lysozyme serves as substrate only for the frog liver sialyltransferase. Lysozyme-phenylazo-N-acetylgalactosamine is active only with the sialyltransferase from bovine submandibular gland. N-Acetylglucosamine derivatives of lysozyme are inactive with all sialyltransferases tested. These observations are discussed in light of the natural substrates for the sialyltransferases investigated.