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.