Sialic acids tissue distribution

The pathway of the biosynthesis of Neu5Ac demonstrates the origin of sialic acids from the cellular hexose and hexosamine pools. These sugars are, therefore, suitable components for the study of the biosynthesis of sialic acid. However, only ManNAc has been shown to be a relatively specific precursor of sialic acids, as may be seen from the distribution of radioactivity between the individual monosaccharides of glycoconjugates after incubation. Injections of radioactive ManNAc into animals, or incubation of surviving tissue slices or individual cells with this compound, give incorporation of label mainly into the sialic acids.226 227... 

Sialidases have a wider distribution in Nature than have the sialic acids. They have been found in a variety of viruses (mainly ortho- and para-myxoviruses) which do not usually contain sialic acids,in many pathogenic and nonpathogcnic bacteria,110-3 10 -30H in several strains of the fungus Streptomyces alhus,309 in such protozoa as Trichomonas foetus,310,311 and in animal, including human, tissues.110,312... 

Beckman et al. (28) have studied the electrophoretic separation of the acid phosphatase activity in tissue extracts on starch gel at pH 8. They described four electrophoretic bands A, B, C, and D. Table IV (28) shows the distribution of activity in different organ extracts. The ABD pattern predominated in kidney BD in liver, intestine, heart, and skeletal muscle B in skin and D in pancreas. The C component was present in a large number of placentae but not in other adult organs. All four electrophoretic components were inhibited by d-(- -)-tartrate A contained sialic acid, D had a lower pH optimum and was more heat resistant than A, B, and C. Components C and D showed parallel electrophoretic behavior. In human skin fibroblasts grown in tissue culture, the acid phosphatase was generally high and the most common pattern was BD. Almost every culture showed some activity. The BD... 

Figure 2. Sialic acid distribution in monosialoganglioside components of various rabbit tissues. Br brain Thy thymus Lu lung St stomach Li liver In intestine Ki kidney Te testis Mu muscle Column height shows percentage distribution of sialic acid in monosialoganglioside fraction. Numbers 1-6 unidentified monosialo-...

Polysialic acid (PSA) is a linear homopolymer of a2-8- or a2-9-linked sialic acid attached to protein scaffolds inclnding the neural cell adhesion molecule (NCAM). Two Golgi-resident polysialyltransferases, PST and STX, are responsible for its synthesis. Although PSA is widely distributed in embryonic tissues, it is normally found only in regenerating neural and muscle tissues in adults. Neo-expression of PSA is often associated with metastatic cancer (115). 

Van Rinsum, J. van Dijk, W. Hooghwinkel, G.J.M. Ferwerda, W. SubceUu-lar localization and tissue distribution of sialic acid precursor-forming enzymes. Biochem. J., 210, 21-28 (1983)... 

Von Rinsum, J., Van Dijk, W., Hoo winkel, GJ.M. Ferwerda, W. (1983) Subcellular Localization and Tissue Distribution of Sialic Acid Precursor-forming Enzymes , BiochemicalJournal, 210, 21-8... 

The aldolase reaction is assumed to be involved mainly in the degradation of the sialic acids, and although the enzyme is widely distributed in mammalian tissues, it occurs sparingly or not at all in mucin-producing tissues. 

Morimoto N, Nakano M, Kinoshita M, Kawabata A, Morita M, Oda Y, Kuroda R, Kakehi K (2001) Specific distribution of sialic acids in animal tissues as examined by LC-ESI-MS after derivatization with l,2-diammo-4,5-methylenedioxybenzene. Anal Chem 73 5422—5428... 

Eash S, Tavares R, Stopa EG, Robbins SH, Brossay L, Atwood WJ. Differential distribution of the JC virus receptor-type sialic acid in normal human tissues. Am Pathol. 2004 164(2) 419 428. 

The different sialic acids exhibit an interesting species- and tissue-specific distribution. However, the biological implications of the various sialic acids and of the different substitution patterns are not fully understood. There is some evidence that different N and O substituents influence enzymic reactions, particularly in the catabolic pathways of sialoglycoconjugates (chapter I). Moreover, effects of substitution of sialic acids on immunological properties of sialoglycoconjugates have been observed (chapter J). Further elucidation of the role of sialic acid modifications remains a challenge for future research. 

Neisseria meningitidis is a pathogen that causes meningitis in humans. It has an unusual capsular homopolysaccharide that is composed of A -acetyl-D-neuraminic acid. The monosaccharide residue has nine carbons (see Fig. 6.20A). It makes up a family of sugar acids called sialic acids that are N- and 0-substituted derivatives (see Chapter 9). The sialic acids are widely distributed and are primarily found at the ends of the oligosaccharide chains attached to glycoproteins that are especially prevalent in bovine and ovine submaxillary mucins, erythrocytes, and nerve tissues. A -acetyl-D-neuraminic acid is biosynthesized by an aldol condensation of pyruvic acid with N-acetyl-D-mannosamine (see Chapter 10). 

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