Glycosyltransferases cell surface

Berger EG, Thumher M Muller U. Galactosyltransferase and sialyltransferase are located in different sub-cellular compartments in HeLa cells. Exp Cell Res (EPB) (1987) 173 267-273. Shur BD Roth S. Cell surface glycosyltransferases. Biochem Biophys Ada (1975) 415 473-512. Schachter H Roden L. The biosynthesis of animal glycoproteins. In Metabolic Conjugation and Metabolic Hydrolysis. WH Fishman, Editor Academic Press New York pp. 1-149. McGuire EJ, Kerlin R, Cebra JJ Roth S. A human milk galactosyltransferase is specific for secreted, but not plasma IgA. J Immunol (1989) 143(9) 2933-2938. 

Shur, B. D., and Roth S., 1975, Cell surface glycosyltransferases, Biochim. Biophys. Acta 415 473. 

Bosmann, H. B., 1972, Cell surface glycosyltransferases and acceptors in normal and RNA- and DNA- virus transformed fibroblasts, Biochem. Biophys. Res. Commun. 48 523. 

How can the many complex polysaccharides found in nature be synthesized Are there genetically determined patterns How are these controlled The answer can be found in the specificities of the hundreds of known glycosyltransferases171 172 and in the patterns of expression of the genes for transferases and other proteins. As a consequence, a great variety of structurally varied polysaccharide structures arise, especially on cell surfaces. The structures are not random but depend upon the assortment of glycosyltransferases available at the particular stage of development in a tissue. 

As already mentioned, formation of glycosidic linkages between monomeric units of the carbohydrate-containing polymers of the bacterial cell-surface is catalyzed by membrane-bound glycosyltransferases, and glycosyl nucleotides are the usual glycosyl donors in the reaction. 

Based on data cited previously it appears that TPA s primary effect is at the cell surface (55, 56). This does not exclude the possibility that TPA is transported and metabolized to an "active" intermediate, which then affects glycosyltransferase activity. However, it is possible (particularly in light of the structural dissimilarity between TPA and RA) that these compounds affect glycoconjugate metabolism in different ways. 

Conformational restriction of biologically flexible molecules is a successful strategy in drug development. Application of this concept to ceramide, the membrane anchor of sphingolipids, led to the unexpected inhibition of glycosyltransferases involved in the combinatorial biosynthesis of gangliosides. This discovery offers a new approach to cell surface engineering. 

Galactosyltransferase is only one member within the broader classification of glycosyltransferases that have been found on cell surfaces these are involved in contact-mediated cell interactions in general, but more specifically are involved in fertilization, morphogenesis, hemostasis, and cell migration. This topic has been well reviewed by Pierce et al. (1980). 

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