Characterization of the Saccharomyces cerevisiae YMR318C (ADH6) gene product as a broad specificity NADPH-dependent alcohol dehydrogenase: relevance in aldehyde reduction.
YMR318C represents an open reading frame from Saccharomyces cerevisiae with unknown function. It possesses a conserved sequence motif, the zinc-containing alcohol dehydrogenase (ADH) signature, specific to the medium-chain zinc-containing ADHs. In the present study, the YMR318C gene product has been purified to homogeneity from overexpressing yeast cells, and found to be a homodimeric ADH, composed of 40 kDa subunits and with a pI of 5.0-5.4. The enzyme was strictly specific for NADPH and was active with a wide variety of substrates, including aliphatic (linear and branched-chain) and aromatic primary alcohols and aldehydes. Aldehydes were processed with a 50-fold higher catalytic efficiency than that for the corresponding alcohols. The highest k(cat)/K(m) values were found with pentanal>veratraldehyde > hexanal > 3-methylbutanal >cinnamaldehyde. Taking into consideration the substrate specificity and sequence characteristics of the YMR318C gene product, we have proposed this gene to be called ADH6. The disruption of ADH6 was not lethal for the yeast under laboratory conditions. Although S. cerevisiae is considered a non lignin-degrading organism, the catalytic activity of ADHVI can direct veratraldehyde and anisaldehyde, arising from the oxidation of lignocellulose by fungal lignin peroxidases, to the lignin biodegradation pathway. ADHVI is the only S. cerevisiae enzyme able to significantly reduce veratraldehyde in vivo, and its overexpression allowed yeast to grow under toxic concentrations of this aldehyde. The enzyme may also be involved in the synthesis of fusel alcohols. To our knowledge this is the first NADPH-dependent medium-chain ADH to be characterized in S. cerevisiae.
Larroy
Carol
C
Department of Biochemistry and Molecular Biology, Faculty of Sciences, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Barcelona), Spain.
Fernández
M Rosario
MR
González
Eva
E
Parés
Xavier
X
Biosca
Josep A
JA
D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001547:Benzaldehydes / Q000378:metabolism; D017353:Gene Deletion; D015870:Gene Expression; D005800:Genes, Fungal; D007526:Isoelectric Point; D007700:Kinetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000447:Aldehydes; D001547:Benzaldehydes; D029701:Saccharomyces cerevisiae Proteins; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase; C446927:ADH6 protein, S cerevisiae; C019642:alcohol dehydrogenase (NADP+); C427725:veratraldehyde