Large Scale Preparation of Natural Glycans

Song, Xuezheng

Abstract

The two major obstacles to progress in glycomics relative to proteomics and genomics are the lack of simple, robust, and automated methods for determining glycan structures and for synthesis of glycans. The net result of this situation is an overall lack of defined glycans for use in functional studies and for use as standards in structural analysis. Significant effort has been directed to the chemo-enzymatic approach to glycan synthesis based on the prediction that the human glycome has a limited number of glycan determinants (~10,000) and that they can be synthesized using available synthetic methods. Synthetic approaches are extremely valuable in generating unique and even complex glycan structures, but knowing what structures to synthesize requires different approaches. Readily available biological materials, which can be rich sources of unique glycans, represent an alternative source of natural glycans; and since they are natural products, they are obviously biologically relevant. If these glycans can be obtained in milligram to gram quantities, natural products become a practical source of reagents for the biomedical community. When function is associated with a glycan, synthetic chemists and fermentation biologists will have targets for producing the large amounts of material required for possible therapeutic applications. We use a functional glycomics approach where ?Shotgun? glycan microarrays display the individual glycans released from a glycome, and we interrogate these arrays with biologically relevant glycan binding proteins to identify corresponding glycan determinants as targets for both structural characterization and chemical synthesis. In order to address the lack of biologically relevant glycans for functional glycomics, we have developed an efficient chemical method based on oxidation with NaOCl (common bleach) that releases all glycans from the glycoconjugates in any biological source to obtain milligram quantities of purified glycans representing the entire glycome that can be printed as shotgun glycan microarrays for functional glycomic studies. Our proprietary, oxidative process eliminates the need for enzymes that are expensive and difficult to scale up and permits us to use kilogram amounts of starting material so that we can obtain even minor glycans comprising <0.1% of the glycome will be available in quantities that will allow them to be purified and structurally characterized. Phase I of this project will develop a kilogram scale process with the ultimate goal in Phase II of developing a true manufacturing processes that will increase this scale by at least an order of magnitude. The company will market purified, biologically relevant and structurally characterized glycans to the research community as free glycans, glycan derivatives, glycan conjugates, glycan derivatized beads, and glycan microarrays for functional glycomic studies. The availability of these reagents to the scientific community will address the major limitation in current glycomic research, which is the lack of available, biologically relevant glycans.

Public Health Relevance

The definitions of the human genome and proteome have led to major advances in our understanding of the function of genes and proteins; but consistent with scientific discovery, this new knowledge reveals the need to understand the structure and function of the glycome, which is comprised of all of the carbohydrate structures synthesized by any organism. This proposed research will combine ?Shotgun? Glycomics, that has been recognized as the first true approach to functional glycomics with a new proprietary method for generating large quantities of biologically relevant glycans for structural and functional analyses. The new technology will be translated into manufacturing process so that these glycans and their derivatives can be commercially available to the biomedical community.