Oligosaccharides sialidases, activity with

Corynebacterium diphtheria,Campylobacter jejuni, and Pasteurella multo-cida Remarkably, the C. jejuni TS exemplifies an oligosaccharide lians-sialidase that specifieally transfers (or hydrolyzes) a-(2— 8)-linkages of siahc acid. The P. multocida enzyme exhibits a-(2—>3) TS activity. Even more striking is the fact drat the latter two baeterial enzymes possess, besides their TS and sialidase activities, additional elassieal sialylliansferase activities with CMP-Neu5Ac as donor. 

New studies have expanded the work of Drzeniek (1972, 1973) with regard to the glycosidic linkage specificity of viral and bacterial sialidases (Corfield et al. 1981 a, b), allowing discrimination between three different viral sialidase activities on the basis of a(2-3) and (2-6) linkages and the nature of the oligosaccharide chain in substrates as described under IV. 3.g). 

Sialidases such as the influenza neuraminidase are retaining enzymes that catalyze the hydrolysis of a-D-A -acetylneuraminic acids from oligosaccharides or glycolipids and glycoproteins. Inhibitors of these enzymes are of great interest since it has been shown that neuraminidase activity can correlate with virulence. ... 

NeuSAc is a weak inhibitor of classical sialidases but does not act at all on the trans-sialidases. Correspondingly, the 2,3-difluoro derivative of NeuSAc, forming a covalent intermediate with sialidases and trans-sialidases (see later) was required at high concentrations (20 mM) to inactivate the enzyme completely Since trans-sialidases possess a lactose-binding site in their active center (as described next), lactose and its derivatives, especially lactitol, inhibit the sialic acid transfer of the enzyme from T. cruzi. Oligosaccharides from the mucins of this trypanosome can also inhibit the transfer of sialic acid to, for example, the substrate A-acetyllactosa-mine. It should be noted that heavy metal ions, especially merciuy, are potent inhibitors of sialidases and trans-sialidases. The latter enzymes do not require calcium ions, in contrast to some siaUdases. " " " ... 

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