Selective Prebiotic Activity of N-glycans Released From Milk Glycoproteins by Novel Endo-beta-N-acetylglucosaminidase

Human milk is the primary source of nutrition for newborns before they are able to digest any other food. Interestingly, some glycosylated milk components are completely indigestible to the infant, and only select gut bacteria possess the enzymes to release and utilize such compounds. Glycans are important biological components involved in the cell-to-cell interaction, signaling, structural integrity, and proper protein formation. Glycans are found linked to other compounds (lipids and proteins) as well as in a free form. Studies on glycosylated proteins indicate that glycans can affect many biological and nutritional properties. However, the challenges in isolation of glycans from glycoproteins have so far limited detailed investigations of these compounds. Glycosidases are widely used for N-glycan release from glycoproteins. The efficient use of glycosidases is essential to scale up the release of these bioactive compounds from protein-rich dairy streams. We recently isolated a novel N-glycosidase that cleaves the N-N'-diacetyl chitobiose moiety found in the N-glycan core of a wide variety of proteins. Sophisticated analytical platforms are enabling food scientists to develop detailed molecular-level understanding of functional compounds in milk and other foods. Mass spectrometry is the preferred technique for glycans analysis as the high mass accuracy improves the ease of identification of compounds based on mass to charge ratio. By determining the microstructures of these compounds, one can determine specific activities associated with the free oligosaccharides as well as the glycoconjugates. Membrane filtration can then be used to scaled-up production and purification of the released glycans. With all these technologies in place, is possible to assess and identify which foods and food streams yield the highest concentrations of functional glycans to obtain the necessary amounts for functional assays and clinical trials. Successful application of the novel enzymes in the dairy industry will allow converting whey, a waste product, into a substrate for selective modulation of the gut microbiota, mimicking what happens in the gut of a healthy breast-fed infant.