Sialyl family

Apart from the 4-O-acetylated sialic acids, another sialidase-resist-ant sialic acid exists in Nature, namely, the internal, Gal-bound, sialic acid residue of GM,. In contrast to this side-positioned sialic acid, the sialyl residues bound to the peripheral Gal of gangliosides, or to both the peripheral and the internal sialic acid residues forming oligo-sialvl chains in several members of the large ganglioside family,la can be readily removed by sialidases, as was tested with viral, bacterial, and mammalian enzymes.35 -35 1... 

C. Foxall, S. R. Watson, D. Dowbenko, C. Fennie, L. A. Lasky, M. Kiso, A. Hasegawa, D. Asa, and B. K. Brandley, The three members of the selectin receptor family recognize a common carbohydrate epitope, the sialyl Lewis X oligosaccharide, J. Cell Biol. 7/7 895 (1992). 

Selectins are a family of membrane glycoproteins that are divalent cation-dependent and bind to specific carbohydrates containing sialylated moieties. They are composed of leukocyte (L)-selectins, endothelial (E)-selectins and platelet (P)-selectins. L-selectins are expressed on most leukocytes, whereas vascular endothelial cells express E-selectins and P-selectins. Initial binding of leukocytes with vascular endothelium involves selectins and consequently they play an important role in leukocyte trafficking. 

Our interest in such methylene acetal derivatives is connected with the design of mimetics of Sialyl Lewis X (sLex) 1, a proposed native ligand for the selectin family of cell adhesion molecules. sLex-selectin interactions have been... 

Many gene products are uncharacterized enzymes that lack a specific class assignment. As discussed in Sect. 2.3, ABPP probes can be used to identify structurally disparate members of enzyme families based on their reactivity with mechanism-based inhibitors. To date, many uncharacterized enzymes have been classified upon their identification via ABPP. For example, the use of a fluorophosphonate probe by Jessani et al. led to the characterization of sialyl acetylesterase - expressed... 

The majority of more recent structures relate to the sialyl Lewis X blood group carbohydrate receptor function for the selectin family of eukaryote lectins that mediate leucocyte-endothelial cell interaction during the initial stages of extravasation ( neutrophil rolling ) (20). These structures are the sialyl Le , Le, and Le sequences and several 6 sulfo GlcNAc and 3 sulfo Gal derivatives found in both protein and sphingolipid glycoconjugates (21-24). 

Sialic acids are a family of nonulosonic acids that have been predominantly found as the outermost carbohydrate units on glycoproteins and glycolipids of vertebrates, or as components of polysaccharides in certain types of bacteria (I, 2). Sialic acids play vital roles in a variety of physiological and pathological processes in vertebrates, such as cellular recognition and communication (1, 2). They are also believed to be important virulence factors in bacteria, used by bacteria to mimic sialylated host cell surface carbohydrate structures to evade detection and attacking by the immune defense mechanisms of the host (3-6). 

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