Endogenous xylose pathway in Saccharomyces cerevisiae.
The baker's yeast Saccharomyces cerevisiae is generally classified as a non-xylose-utilizing organism. We found that S. cerevisiae can grow on D-xylose when only the endogenous genes GRE3 (YHR104w), coding for a nonspecific aldose reductase, and XYL2 (YLR070c, ScXYL2), coding for a xylitol dehydrogenase (XDH), are overexpressed under endogenous promoters. In nontransformed S. cerevisiae strains, XDH activity was significantly higher in the presence of xylose, but xylose reductase (XR) activity was not affected by the choice of carbon source. The expression of SOR1, encoding a sorbitol dehydrogenase, was elevated in the presence of xylose as were the genes encoding transketolase and transaldolase. An S. cerevisiae strain carrying the XR and XDH enzymes from the xylose-utilizing yeast Pichia stipitis grew more quickly and accumulated less xylitol than did the strain overexpressing the endogenous enzymes. Overexpression of the GRE3 and ScXYL2 genes in the S. cerevisiae CEN.PK2 strain resulted in a growth rate of 0.01 g of cell dry mass liter(-1) h(-1) and a xylitol yield of 55% when xylose was the main carbon source.
Toivari
Mervi H
MH
VTT Biotechnology, FIN-02044 VTT, Finland. Mervi.Toivari@vtt.fi
Salusjärvi
Laura
L
Ruohonen
Laura
L
Penttilä
Merja
M
D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D050542:D-Xylulose Reductase; D010843:Pichia / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014993:Xylitol / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
D003470:Culture Media; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014994:Xylose; D013401:Sugar Alcohol Dehydrogenases; D000449:Aldehyde Reductase; D050542:D-Xylulose Reductase; D014993:Xylitol