title: Improving lycopene production in Escherichia coli by engineering metabolic control.
abstract: Metabolic engineering has achieved encouraging success in producing foreign metabolites in a variety of hosts. However, common strategies for engineering metabolic pathways focus on amplifying the desired enzymes and deregulating cellular controls. As a result, uncontrolled or deregulated metabolic pathways lead to metabolic imbalance and suboptimal productivity. Here we have demonstrated the second stage of metabolic engineering effort by designing and engineering a regulatory circuit to control gene expression in response to intracellular metabolic states. Specifically, we recruited and altered one of the global regulatory systems in Escherichia coli, the Ntr regulon, to control the engineered lycopene biosynthesis pathway. The artificially engineered regulon, stimulated by excess glycolytic flux through sensing of an intracellular metabolite, acetyl phosphate, controls the expression of two key enzymes in lycopene synthesis in response to flux dynamics. This intracellular control loop significantly enhanced lycopene production while reducing the negative impact caused by metabolic imbalance. Although we demonstrated this strategy for metabolite production, it can be extended into other fields where gene expression must be closely controlled by intracellular physiology, such as gene therapy.
authors.affiliation: Department of Chemical Engineering, University of California Los Angeles, Los Angeles, CA 90034, USA.
authors.forename: W R
authors.initials: WR
authors.lastname: Farmer
authors.forename: J C
authors.initials: JC
authors.lastname: Liao
mesh_terms: D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000096:biosynthesis / Q000235:genetics; D016588:Anticarcinogenic Agents / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism; D001426:Bacterial Proteins; D019748:Carbon-Carbon Double Bond Isomerases / Q000096:biosynthesis / Q000235:genetics; D002338:Carotenoids / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005246:Feedback; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D005818:Genetic Engineering / Q000379:methods*; D006019:Glycolysis; D045782:Hemiterpenes; D000077276:Lycopene; D008660:Metabolism / Q000235:genetics; D009584:Nitrogen / Q000172:deficiency; D010755:Organophosphates / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D010749:Phosphoprotein Phosphatases / Q000235:genetics; D017866:Phosphotransferases (Paired Acceptors) / Q000096:biosynthesis / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics; D018085:Regulon; D015534:Trans-Activators; D014157:Transcription Factors
chemical_list: D016588:Anticarcinogenic Agents; D000975:Antioxidants; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D045782:Hemiterpenes; D010755:Organophosphates; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D002338:Carotenoids; C011632:acetyl phosphate; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D011494:Protein Kinases; C055699:protein kinase-phosphatase NTRB; D017866:Phosphotransferases (Paired Acceptors); C022509:pyruvate, water dikinase; D010749:Phosphoprotein Phosphatases; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase; D009584:Nitrogen; D000077276:Lycopene