Plant N-glycan breakdown by human gut Bacteroides

The major nutrients available to the human colonic microbiota are complex glycans derived from the diet. To degrade this highly variable mix of sugar structures, gut microbes have acquired a huge array of different carbohydrate-active enzymes (CAZymes), predominantly glycoside hydrolases, many of which have specificities that can be exploited for a range of different applications. Plant N-glycans are prevalent on proteins produced by plants and thus components of the diet, but the breakdown of these complex molecules by the gut microbiota has not been explored. Plant N-glycans are also well characterized allergens in pollen and some plant-based foods, and when plants are used in heterologous protein production for medical applications, the N-glycans present can pose a risk to therapeutic function and stability. Here we use a novel genome association approach for enzyme discovery to identify a breakdown pathway for plant complex N-glycans encoded by a gut Bacteroides species and biochemically characterize five CAZymes involved, including structures of the PNGase and GH92 α-mannosidase. These enzymes provide a toolbox for the modification of plant N-glycans for a range of potential applications. Furthermore, the keystone PNGase also has activity against insect-type N-glycans, which we discuss from the perspective of insects as a nutrient source

Expression of Peptide- and Glycopeptide Modifying Glycosyltransferases for Applications in Liquid- and Solid Phase Carbohydrate Synthesis

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Influenza Neuraminidase Inhibitors: Synthetic Approaches, Derivatives and Biological Activity

Despite being a common viral disease, influenza has very negative consequences, causing the death of around half a million people each year. A neuraminidase located on the surface of the virus plays an important role in viral reproduction by contributing to the release of viruses from infected host cells. The treatment of influenza is mainly based on the administration of neuraminidase inhibitors. The neuraminidase inhibitors zanamivir, laninamivir, oseltamivir and peramivir have been commercialized and have been demonstrated to be potent influenza viral neuraminidase inhibitors against most influenza strains. In order to create more potent neuraminidase inhibitors and fight against the surge in resistance resulting from naturally-occurring mutations, these anti-influenza drugs have been used as templates for the development of new neuraminidase inhibitors through structure-activity relationship studies. Here, we review the synthetic routes to these commercial drugs, the modifications which have been performed on these structures and the effects of these modifications on their inhibitory activity

Changes in protein N-glycosylation during the fruit development and ripening in melting-type peach

The posttranslational modification of proteins with complex carbohydrate moieties (glycosylation) regulates the process of fruit ripening. Exoglycosidases are enzymes that can trim this protein glycosylation and are therefore considered to be important targets in the control of fruit ripening and softening. Melting-type peaches are popular seasonal fruits in many Asian regions, but the extremely short shelf-life of the peach fruits significantly hampers their economic value. To investigate the effect of the protein glycosylation and exoglycosidase activities on the development and ripening of the peach fruit, the fruit flesh of the melting peach cultivar 'Xia hui 6' at five different maturity stages were analyzed. The N-glycan profile of each sample was characterized and quantified by HILIC-UPLC and MALDI-TOF mass spectrometry, revealing two characteristic N-glycan structures (MMXF and GnGnMXF) which were strongly affected by the state of maturity. Furthermore, it was shown that one of the endogenous exoglycosidase activities analyzed (β-N-acetylhexosaminidase, β-Hex) correlated with the MMXF and GnGnMXF N-glycan structures (p < 0.05) in an obverse manner. These findings lay the foundation for further elucidation of the physiological functions of protein glycosylation in peach fruit development and ripening