The sialate
| Autor: | Lloyd S, Robinson, Warren G, Lewis, Amanda L, Lewis |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
O-acetylation
O-acetyl esterase Neuraminidase Glycobiology and Extracellular Matrices Escherichia coli (E. coli) microbiome Bacteroides thetaiototaomicron Streptococcus agalactiae Substrate Specificity Bacteroides fragilis Bacterial Proteins mucin mucus Animals Intestinal Mucosa Bacteroidetes Hydrolysis sialidase Polysaccharides Bacterial Mucins Acetylation Hydrogen-Ion Concentration N-Acetylneuraminic Acid Recombinant Proteins Gastrointestinal Microbiome carbohydrates (lipids) Bacteroides thetaiotaomicron sialic acid Enterohemorrhagic Escherichia coli Microbial Interactions Cattle Carboxylic Ester Hydrolases |
| Zdroj: | The Journal of Biological Chemistry |
| ISSN: | 1083-351X |
| Popis: | The gut harbors many symbiotic, commensal, and pathogenic microbes that break down and metabolize host carbohydrates. Sialic acids are prominent outermost carbohydrates on host glycoproteins called mucins and protect underlying glycan chains from enzymatic degradation. Sialidases produced by some members of the colonic microbiota can promote the expansion of several potential pathogens (e.g. Clostridium difficile, Salmonella, and Escherichia coli) that do not produce sialidases. O-Acetyl ester modifications of sialic acids help resist the action of many sialidases and are present at high levels in the mammalian colon. However, some gut bacteria, in turn, produce sialylate-O-acetylesterases to remove them. Here, we investigated O-acetyl ester removal and sialic acid degradation by Bacteroidetes sialate-O-acetylesterases and sialidases, respectively, and subsequent utilization of host sialic acids by both commensal and pathogenic E. coli strains. In vitro foraging studies demonstrated that sialidase-dependent E. coli growth on mucin is enabled by Bacteroides EstA, a sialate O-acetylesterase acting on glycosidically linked sialylate-O-acetylesterase substrates, particularly at neutral pH. Biochemical studies suggested that spontaneous migration of O-acetyl esters on the sialic acid side chain, which can occur at colonic pH, may serve as a switch controlling EstA-assisted sialic acid liberation. Specifically, EstA did not act on O-acetyl esters in their initial 7-position. However, following migration to the 9-position, glycans with O-acetyl esters became susceptible to the sequential actions of bacterial esterases and sialidases. We conclude that EstA specifically unlocks the nutritive potential of 9-O-acetylated mucus sialic acids for foraging by bacteria that otherwise are prevented from accessing this carbon source. |
| Databáze: | OpenAIRE |
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