Abstract:
Sugars play important roles in multiple different contexts beyond that of central metabolism. In addition to their presence in structures such as the cellulose of plant cell walls, sugars coat every cell in our body, where they serve roles in intercellular recognition, including important immune responses. These sugars are all installed and removed by enzymes that have evolved for their specific task. Accordingly, carbohydrate-active enzymes can have great value in industrial and medical applications but their discovery can be a challenge. In this seminar I shall discuss our recent development and application of high-throughput approaches for the discovery of novel carbohydrate-active enzymes. Our approach is based upon the production of large “metagenomic” libraries of genes and then screening of bacteria carrying these genes using high throughput methodologies. Our initial approaches allowed us to screen ~20,000 per day but using our new microfluidic nano-droplet approaches we can now screen millions per day. I shall illustrate our approach with two examples. One involves our discovery of enzymes that allow us to change the ABO blood type of donated red blood cells or human organs, thereby improving access to blood and organs. In collaboration with Jay Kizhakkedathu and others we have founded a company, Avivo Biomedical Inc., to bring the technology through regulatory approval. My second example is one in which we designed a screen to identify enzymes that use unusual mechanisms to cleave glycosidic bonds. In this way we have identified and characterized, both mechanistically and structurally, a relatively commonly occurring alternative pathway for glycoside degradation that has unprecedentedly broad specificity.