Subsystem: Sialic Acid Metabolism
This subsystem's description is:
Sialic acid occupies the terminal position within glycan molecules on the surfaces of many vertebrate cells, where it functions in diverse cellular processes such as intercellular adhesion and cell signalling. Pathogenic bacteria have evolved to use this molecule beneficially in at least two different ways: they can coat themselves in sialic acid, providing resistance to components of the host's innate immune response, or they can use it as a nutrient. Sialic acid itself is either synthesized de novo by these bacteria or scavenged directly from the host.
The sialic acids are a family of sugars with a shared nine-carbon backbone, a carboxylic acid at the C1 position, and various alpha-glycosidic linkages to the underlying sugar chain (R) from the C2 position. Various substitutions at the C4, C5, C7, C8 and C9 positions combine with linkage variation to generate the diversity of sialic acids in nature. Sialic acids are typically found at the terminal position of N- and O-linked glycans attached to the cell surface and to secreted glycoproteins, as well as on glycosphingolipids expressed at the cell surface.
1.0 - Organisms that synthesize sialic acid de novo but do not catabolize it (like all Campylobacter);
2.0 - Organisms that catabolize but do not synthesize (use exogenous sialic acids);
3.0 - Organisms that both catabolize sialic acid and synthesize it de novo from simple metabolites;
4.0 - Organisms that both catabolize exogenous sialic acid and use for surface decortion (precursor scavenging -Haemophilus influenzae );
5.0 - Organisms that just use exogenous sialic acids for surface decoration;
x - stands for a missing gene in the pathway
For more information, please check out the description and the additional notes tabs, below
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