title: Engineering cytosolic acetyl-coenzyme A supply in Saccharomyces cerevisiae: Pathway stoichiometry, free-energy conservation and redox-cofactor balancing.
abstract: Saccharomyces cerevisiae is an important industrial cell factory and an attractive experimental model for evaluating novel metabolic engineering strategies. Many current and potential products of this yeast require acetyl coenzyme A (acetyl-CoA) as a precursor and pathways towards these products are generally expressed in its cytosol. The native S. cerevisiae pathway for production of cytosolic acetyl-CoA consumes 2 ATP equivalents in the acetyl-CoA synthetase reaction. Catabolism of additional sugar substrate, which may be required to generate this ATP, negatively affects product yields. Here, we review alternative pathways that can be engineered into yeast to optimize supply of cytosolic acetyl-CoA as a precursor for product formation. Particular attention is paid to reaction stoichiometry, free-energy conservation and redox-cofactor balancing of alternative pathways for acetyl-CoA synthesis from glucose. A theoretical analysis of maximally attainable yields on glucose of four compounds (n-butanol, citric acid, palmitic acid and farnesene) showed a strong product dependency of the optimal pathway configuration for acetyl-CoA synthesis. Moreover, this analysis showed that combination of different acetyl-CoA production pathways may be required to achieve optimal product yields. This review underlines that an integral analysis of energy coupling and redox-cofactor balancing in precursor-supply and product-formation pathways is crucial for the design of efficient cell factories.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Harmen M
authors.initials: HM
authors.lastname: van Rossum
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Barbara U
authors.initials: BU
authors.lastname: Kozak
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Jack T
authors.initials: JT
authors.lastname: Pronk
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. Electronic address: A.J.A.vanMaris@tudelft.nl.
authors.forename: Antonius J A
authors.initials: AJA
authors.lastname: van Maris
mesh_terms: D000105:Acetyl Coenzyme A / Q000096:biosynthesis* / Q000235:genetics*; D053898:Biosynthetic Pathways / Q000502:physiology; D003067:Coenzymes / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D024861:Genetic Enhancement / Q000379:methods; D060847:Metabolic Engineering / Q000379:methods*; D064688:Metabolic Flux Analysis; D053858:Metabolic Networks and Pathways / Q000502:physiology; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D003067:Coenzymes; D017382:Reactive Oxygen Species; D029701:Saccharomyces cerevisiae Proteins; D000105:Acetyl Coenzyme A
keywords: ATP-citrate lyase; Acetylating acetaldehyde dehydrogenase; Carnitine shuttle; Phosphoketolase; Pyruvate dehydrogenase; Pyruvate-formate lyase