Stereochemistry of furfural reduction by a Saccharomyces cerevisiae aldehyde reductase that contributes to in situ furfural detoxification.
Ari1p from Saccharomyces cerevisiae, recently identified as an intermediate-subclass short-chain dehydrogenase/reductase, contributes in situ to the detoxification of furfural. Furfural inhibits efficient ethanol production by yeast, particularly when the carbon source is acid-treated lignocellulose, which contains furfural at a relatively high concentration. NADPH is Ari1p's best known hydride donor. Here we report the stereochemistry of the hydride transfer step, determined by using (4R)-[4-(2)H]NADPD and (4S)-[4-(2)H]NADPD and unlabeled furfural in Ari1p-catalyzed reactions and following the deuterium atom into products 2-furanmethanol or NADP(+). Analysis of the products demonstrates unambiguously that Ari1p directs hydride transfer from the si face of NADPH to the re face of furfural. The singular orientation of substrates enables construction of a model of the Michaelis complex in the Ari1p active site. The model reveals hydrophobic residues near the furfural binding site that, upon mutation, may increase specificity for furfural and enhance enzyme performance. Using (4S)-[4-(2)H]NADPD and NADPH as substrates, primary deuterium kinetic isotope effects of 2.2 and 2.5 were determined for the steady-state parameters k(cat)(NADPH) and k(cat)/K(m)(NADPH), respectively, indicating that hydride transfer is partially rate limiting to catalysis.
U.S. Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604, USA. Michael.Bowman@ars.usda.gov
Michael J
MJ
Bowman
Douglas B
DB
Jordan
Karl E
KE
Vermillion
Jay D
JD
Braker
Jaewoong
J
Moon
Z Lewis
ZL
Liu
D000449:Aldehyde Reductase / Q000378:metabolism*; D001711:Biotransformation; D005662:Furaldehyde / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013237:Stereoisomerism
D029701:Saccharomyces cerevisiae Proteins; D009249:NADP; D005662:Furaldehyde; D000449:Aldehyde Reductase