|MOON, JAEWOONG - Xyleco, Inc|
Submitted to: Yeast
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2015
Publication Date: 2/26/2015
Publication URL: http://handle.nal.usda.gov/10113/60668
Citation: Moon, J., Liu, Z.L. 2015. Direct enzyme assay evidence confirms aldehyde reductase function of Ydr541cp and Ygl039wp from Saccharomyces cerevisiae. Yeast. 32:399-407.
Interpretive Summary: Aldehyde inhibitors are commonly encountered during biomass fermentation processes and overcoming the challenges of these toxic compounds is critical for a sustainable biofuels production. Numerous identified tolerance candidate genes for yeast are uncharacterized and there functions are unknown. Recognition of an aldehyde reduction function in tolerant yeast is particularly significant from both basic and applied science perspective. ARS scientists recently discovered a novel aldehyde reduction gene and comprehensively characterized the protein’s enzyme kinetics and stereochemistry. In this study, proteins encoded by two candidate tolerance genes were isolated and their strong specific enzyme activity toward 14 aldehyde substrates involved in biomass fermentation processes was demonstrated. Along with a recently well characterized aldehyde reductase gene ARI1, we report an aldehyde reductase gene family in Saccharomyces cerevisiae with at least four gene members. These results on identification of members of the aldehyde reduction gene family not only contribute to annotation of the yeast genome, but also aid tolerant strain development of the next-generation biocatalyst for advanced biofuels production from lignocellulosic materials.
Technical Abstract: Aldehyde reductase gene ARI1 is a recently characterized member of intermediate subfamily under SDR (short-chain dehydrogenase/reductase) superfamily that revealed mechanisms of in situ detoxification of furfural and HMF for tolerance of Saccharomyces cerevisiae. Uncharacterized open reading frames (ORF) are common among the identified tolerant candidate genes for lignocellulose-to-advanced biofuels conversion. This report presents proteins of two functionally unknown ORFs, YDR541C and YGL039W, and direct enzyme assay against aldehyde inhibitory compounds that are commonly encountered during lignocellulosic biomass fermentation processes. Each of the partially purified proteins encoded by these ORFs showed a molecular mass at approximately 38 kDa that similar to Ari1p, a protein encoded by aldehyde reductase gene. Both proteins demonstrated strong aldehyde reduction activities toward 14 aldehyde substrates with high levels of reduction activity for Ydr541cp toward both aromatic and aliphatic aldehydes. While Ydr541cp was observed to have a significantly higher specific enzyme activity at 20 U/mg using co-factor NADPH, Ygl039wp displayed a NADH preference at 25 U/mg in reduction of butylaldehyde. Amino acid sequence analysis identified a characteristic catalytic triad, Ser, Tyr and Lys; a conserved catalytic motif of Tyr-X-X-X-Lys; and a cofactor-binding sequence motif Gly-X-X-Gly-X-X-Ala near the N-terminus that are shared by Ydr541cp, Ygl039wp, Yol151wp/GRE2, and Ari1p. Our results suggest an aldehyde reductase gene family exists in S. cerevisiae including at least these 4 genes. This finding contributes to the yeast gene annotation and aids development of the next-generation biocatalyst for advanced biofuels production.