Engineering cytosolic acetyl-coenzyme A supply in Saccharomyces cerevisiae: Pathway stoichiometry, free-energy conservation and redox-cofactor balancing

• Published in: Metabolic engineering Vol. 36; pp. 99 - 115
• Main Authors: van Rossum, Harmen M., Kozak, Barbara U., Pronk, Jack T., van Maris, Antonius J.A.
• Format: Journal Article
• Language: English
• Published: Belgium Elsevier Inc 01.07.2016
• Subjects: Acetyl Coenzyme A - biosynthesis; Acetyl Coenzyme A - genetics; Acetylating acetaldehyde dehydrogenase; ATP-citrate lyase; Biosynthetic Pathways - physiology; Carnitine shuttle; Coenzymes - genetics; Coenzymes - metabolism; Cytosol - metabolism; Energy Metabolism - physiology; Genetic Enhancement - methods; Metabolic Engineering - methods; Metabolic Flux Analysis; Metabolic Networks and Pathways - physiology; Oxidation-Reduction; Phosphoketolase; Pyruvate dehydrogenase; Pyruvate-formate lyase; Reactive Oxygen Species - metabolism; Saccharomyces cerevisiae - physiology; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; R(ibose-)5-P; γS; E(rythrose-)4P; A-ALD; ADH; X(ylulose-)5P; FPR; F1,6P; FDH; S7P; PDC; P; Acetylating acetaldehyde dehydrogenase; Ach1; FeS; PDH; TPP; PFL; PFO; Pi; Pyruvate dehydrogenase; Phosphoketolase; LSC; Pyruvate-formate lyase; F6P; PDH bypass; Ribulose-5-P; acetyl-P; PPi; ACL; CIT; ACS; Carnitine shuttle; G(lyceraldehyde-)3P; ΔGR; TCA; γ; CoA; CAT; fructose-6-P; POX; ALD; acetyl-CoA; PK; PTA; γP; ATP-citrate lyase
• DOI: 10.1016/j.ymben.2016.03.006
• ISSN: 1096-7176

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. •Precursor supply strongly influences the yield of acetyl-CoA-derived products on sugars.•The native yeast pathway for cytosolic acetyl-CoA formation is ATP inefficient.•Pathways from glucose to acetyl-CoA have different ATP, NAD(P)H and carbon stoichiometries.•Optimal pathway configuration for acetyl-CoA generation is strongly product dependent.•Combinations of acetyl-CoA forming reactions should be considered in pathway design.