On the role of GAPDH isoenzymes during pentose fermentation in engineered Saccharomyces cerevisiae.
In the metabolic network of the cell, many intermediary products are shared between different pathways. d-Glyceraldehyde-3-phosphate, a glycolytic intermediate, is a substrate of GAPDH but is also utilized by transaldolase and transketolase in the scrambling reactions of the nonoxidative pentose phosphate pathway. Recent efforts to engineer baker's yeast strains capable of utilizing pentose sugars present in plant biomass rely on increasing the carbon flux through this pathway. However, the competition between transaldolase and GAPDH for d-glyceraldehyde-3-phosphate produced in the first transketolase reaction compromises the carbon balance of the pathway, thereby limiting the product yield. Guided by the hypothesis that reduction in GAPDH activity would increase the availability of d-glyceraldehyde-3-phosphate for transaldolase and thereby improve ethanol production during fermentation of pentoses, we performed a comprehensive characterization of the three GAPDH isoenzymes in baker's yeast, Tdh1, Tdh2, and Tdh3 and analyzed the effect of their deletion on xylose utilization by engineered strains. Our data suggest that overexpression of transaldolase is a more promising strategy than reduction in GAPDH activity to increase the flux through the nonoxidative pentose phosphate pathway.
Institute for Molecular Bioscience, Goethe University, Frankfurt, Germany.
Annabell
A
Linck
Xuan-Khang
XK
Vu
Christine
C
Essl
Charlotte
C
Hiesl
Eckhard
E
Boles
Mislav
M
Oreb
D005285:Fermentation; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering; D010429:Pentoses / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014153:Transaldolase / Q000378:metabolism
D007527:Isoenzymes; D010429:Pentoses; D029701:Saccharomyces cerevisiae Proteins; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); C465224:TDH1 protein, S cerevisiae; C465225:TDH2 protein, S cerevisiae; C465226:TDH3 protein, S cerevisiae; D014153:Transaldolase
GAPDH kinetics; Saccharomyces cerevisiae; glyceraldehyde-3-phosphate; pentose; sedoheptulose-7-phosphate accumulation; transaldolase