The release of N-acetyl- and N-glycolloyl-neuraminic acid from soluble complex carbohydrates and erythrocytes by bacterial, viral and mammalian sialidases

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Abstract
A series of substrates, sialyl(2 .fwdarw. 3)lactose, sialyl(2 .fwdarw. 6)GalNAc and ganglioside GM3, containing either N-acetylneuraminic acid (AcNeu) or N-glycolloylneuraminic acid (GcNeu), was prepared. The trisaccharide GcNeu(2 .fwdarw. 3)lactose was prepared by ozonolysis of GcNeu-GM3 and the disaccharides AcNeu(2 .fwdarw. 6)GalNAc and GcNeu(2 .fwdarw. 6)GalNAc were isolated from bovine submandibular-gland mucin by alkali elimination. Sialidases from Newcastle-disease virus, fowl-plague virus, influenza virus A2, Clostridium perfringens, Vibrio cholerae, Arthrobacter ureafaciens and human liver lysosomes were studied with the above substrates and all showed poorer cleavage of GcNeu-containing substrates when compared with the corresponding AcNeu-containing compounds. This was reflected in the Km was Vmax values of these sialidases. Differences between viral and bacterial sialidases could be detected on the basis of their kinetic constants and time curves of sialic acid release. Preferred release of AcNeu relative to GcNeu was also observed with bovine submandibular gland mucin and a mixture of human and porcine erythrocytes, macromolecular substrates containing both AcNeu and GcNeu. The significance of differential cleavage of AcNeu and GcNeu by sialidases is considered together with examples of the role of GcNeu in physiological systems.