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.

This study focused on the inhibitory effects of wheat bran feruloyl oligosaccharides (FOs) on the formation of AGEs in three bovine serum albumin (BSA)-based non-enzymatic glycation models, namely BSA-fructose, BSA-methylglyoxal (MGO), and BSA-glyoxal (GO). In the BSA-fructose model, FOs at 0.25 mg/mL achieved a 62% inhibition rate of fructosamine, equivalent to approximately 78% of the activity of the positive control aminoguanidine (AG), and reduced fluorescent AGEs by over 50% on day 12. Additionally, FOs suppressed the accumulation of α-dicarbonyl compounds, key intermediates in the glycation pathway. In the BSA-MGO and BSA-GO system, the decreased fluorescence intensity of tryptophan residues indicated that FOs bound to BSA, inducing conformational changes in the protein microenvironment; this binding also inhibited protein carbonyl formation and the loss of thiol groups, thereby modulating the protein glycation process. Compared with their precursors (ferulic acid, FA; xylooligosaccharides, XOS), FOs exhibited comparable or even superior inhibitory activity against specific AGE subtypes, suggesting a synergistic effect between the feruloyl and oligosaccharide moieties. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that FOs reduced the band intensity of 90 kDa AGEs in the glycation system, indicating the inhibition of protein-fructose cross-linking. Fluorescence spectroscopy confirmed that FOs dynamically quenched BSA with a single binding site, and thermodynamic calculations demonstrated that the binding was spontaneous (ΔG < 0), primarily driven by hydrogen bonds and van der Waals forces (ΔH < 0, ΔS < 0). This study systematically investigated the anti-glycation activities of FOs and their precursors. The findings demonstrate that FOs are promising natural glycation inhibitors and provide important theoretical and experimental support for related research. Furthermore, this study establish a basis for the green and high-value utilization of agricultural by-products like wheat bran.