Monday, May 4, 2009
11-24
Engineering of Saccharomyces cerevisiae metabolism for high-level and energy-independent production of cytosolic acetyl-CoA
Christian Weber1, Jelena Duvnjak1, Gunter Festel2, and Eckhard Boles1. (1) Institute of Molecular Biosciences, Goethe-University Frankfurt, Max-von-Laue-Str. 9, Frankfurt, D-60438, Germany, (2) Butalco GmbH, Schuermattstrasse 1, Huenenberg, CH-6331, Switzerland
Acetyl-CoA is an important metabolite that participates in many biochemical reactions and is a central precursor for a number of interesting biobased chemicals and biofuels (e.g. n-butanol, industrial chemicals derived from fatty acid biosynthesis, isoprenoids, secondary metabolites). In S. cerevisiae large amounts of acetyl-CoA are synthesized from pyruvate by oxidative decarboxylation by the mitochondrial multienzyme complex pyruvate dehydrogenase (PDH). However, in yeast mitochondrial acetyl-CoA cannot be exported to the cytosol. Alternatively, yeast can convert pyruvate to acetyl-CoA in the cytosol via acetaldehyde and acetate. The enzymes involved in this so-called “bypass” pathway are pyruvate decarboxylase, acetaldehyde dehydrogenase and acetyl-CoA synthetase (ACS). However, the last reaction catalysed by ACS is energized by the conversion of ATP to AMP and makes fermentative processes less energy efficient leading to decreased cell and product yields. Moreover, the cytosolic concentrations of acetyl-CoA produced by this pathway are very low and limit the production of follow-up metabolites. In order to increase the cytosolic acetyl-CoA pool we engineered a new energy-independent pyruvate dehydrogenase bypass by overproduction of the CoA-dependent acetaldehyde dehydrogenases MhpF or AdhE from E. coli. This invention will be applicable for a broad range of fermentative conversion processes with yeast, especially for the production of butanol and hydrocarbon biofuels.
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