A Parsimonious Mechanism of Sugar Dehydration by Human GDP-Mannose-4,6-dehydratase.

Authors:
Martin Pfeiffer
Martin Pfeiffer
Max-Planck Institute for Molecular Biomedicine
Germany
Catrine Johansson
Catrine Johansson
University of Oxford
Tobias Krojer
Tobias Krojer
University of Oxford
United Kingdom
Kathryn L Kavanagh
Kathryn L Kavanagh
University of Oxford
United Kingdom
Udo Oppermann
Udo Oppermann
University of Oxford
United Kingdom
Bernd Nidetzky
Bernd Nidetzky
Graz University of Technology
Austria

ACS Catal 2019 Apr 1;9(4):2962-2968. Epub 2019 Mar 1.

Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, 8010 Graz, Austria.

Biosynthesis of 6-deoxy sugars, including l-fucose, involves a mechanistically complex, enzymatic 4,6-dehydration of hexose nucleotide precursors as the first committed step. Here, we determined pre- and postcatalytic complex structures of the human GDP-mannose 4,6-dehydratase at atomic resolution. These structures together with results of molecular dynamics simulation and biochemical characterization of wildtype and mutant enzymes reveal elusive mechanistic details of water elimination from GDP-mannose C5″ and C6″, coupled to NADP-mediated hydride transfer from C4″ to C6″. We show that concerted acid-base catalysis from only two active-site groups, Tyr and Glu, promotes a 1,4-elimination from an enol (not an enolate) intermediate. We also show that the overall multistep catalytic reaction involves the fewest position changes of enzyme and substrate groups and that it proceeds under conserved exploitation of the basic (minimal) catalytic machinery of short-chain dehydrogenase/reductases.

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Source
http://pubs.acs.org/doi/10.1021/acscatal.9b00064
Publisher Site
http://dx.doi.org/10.1021/acscatal.9b00064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454399PMC
April 2019
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