Deoxysugars are special carbohydrates lacking at least one hydroxy group. They are important building blocks and recognition sites in functional oligosaccharides, glycoconjugates and natural glycosides (e.g. antibiotics), in which they often critically affect bioactivity. Deoxygenation of common sugars typically happens at nucleotide sugar level and is catalyzed by 4,6-dehydratases that belong to the short-chain dehydrogenases/reductases (SDRs). Natural deoxysugar synthesis is restricted to only a few highly specialized pathways, which are biologically separated due to high specificities of the involved SDRs, hampering synthetic biology options to create artificial pathways towards new deoxy sugar nucleotides. Important opportunities for deoxysugar synthesis could arise via specificity engineering of SDRs, which remains a fundamental challenge due to subtle structure-function relationships. This project aims to develop new SDRs (dehydratase, epimerase, reductase) that show programmable reactivity and specificity, allowing more flexibility in synthetic cascades. Deeper fundamental understanding of SDRs guides our engineering approach, aiming to 1) broaden substrate
acceptance/selectivity and 2) elicit another reactivity in an enzyme with desired substrate scope via a combination of focused mutagenesis and detailed biochemical/mechanistic analysis. As a practical target, a novel synthetic pathway from sucrose to UDP-Lfucose will be designed, based on engineered SDR enzymes.