The Natural Occurrence of Sialic Acids

Sialic acid has been reported in an arborvirus, the Sindbis virus. The envelope membrane of this virus consists of a lipid and a protein containing 14% carbohydrate. The sialic acid present probably occupies the terminal positions of at least the largest carbohydrate chains (Strass et aL, 1970 Burge and Strass, 1970). While the membrane protein core 

SAI-SUN NG and JOEL A. DAIN Department of Biochemistry, University of Rhode Island, Kingston, Rhode Island 02881. 

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The wide occurrence of sialic acids in nature is an indication of their great biological importance. As is described in other chapters in this book, the identification of the sialic acids was pioneered in several laboratories, while the biosynthetic mechanism of sialic acid formation was elucidated essentially by the work of Roseman s and Warren s groups in the United States (see Roseman 1962, Warren 1972, Schachter and Roden 1973, McGuire 1976, Schachter 1978). 

Echinoderms constitute a peculiar phylum of invertebrates belonging to the most highly organized animals, the Deuterostomia, including, also, all the phyla of chordates. Among the invertebrates, echinoderms are the richest in glycolipids, and differ from all of the other marine invertebrate phyla in that they contain sialoglycolipids.79 This conforms to the data of Warren, who studied the occurrence of sialic acids in Nature, and found that all of the vertebrates have them, but, of the invertebrates, only the echinoderms practically all of the Protostomia contain no sialic acids.274... 

The occurrence of sialic acids in nature is presented in section XII in the form of a phylogenetic chart (Fig. 1). This serves as a basis for comparison in the... 

The name sialic acid" has been given to the several nonulosaminic acids isolated from the submaxillary mucoproteins, although the chemical composition of these varies with the species source. Svennerholm has proposed that the name sialic acid be restricted to the basic structure common to all these various sialic acids thus ovine sialic acid" would be designated Af-acetylsialic acid. However since this basal component, here termed sialic acid, is identical with neuraminic acid, it would seem more appropriate to adopt the name neuraminic acid for the parent add and to retain the name sialic acid to denote the various mono- and di-acyl neuraminic acids of natural occurrence in mucoproteins, regardless of their source. This is the convention which has been used in referring to the various nonulosaminic acids in Table I and thoughout this article. ... 

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