title: Combining metabolic and protein engineering of a terpenoid biosynthetic pathway for overproduction and selectivity control.
abstract: A common strategy of metabolic engineering is to increase the endogenous supply of precursor metabolites to improve pathway productivity. The ability to further enhance heterologous production of a desired compound may be limited by the inherent capacity of the imported pathway to accommodate high precursor supply. Here, we present engineered diterpenoid biosynthesis as a case where insufficient downstream pathway capacity limits high-level levopimaradiene production in Escherichia coli. To increase levopimaradiene synthesis, we amplified the flux toward isopentenyl diphosphate and dimethylallyl diphosphate precursors and reprogrammed the rate-limiting downstream pathway by generating combinatorial mutations in geranylgeranyl diphosphate synthase and levopimaradiene synthase. The mutant library contained pathway variants that not only increased diterpenoid production but also tuned the selectivity toward levopimaradiene. The most productive pathway, combining precursor flux amplification and mutant synthases, conferred approximately 2,600-fold increase in levopimaradiene levels. A maximum titer of approximately 700 mg/L was subsequently obtained by cultivation in a bench-scale bioreactor. The present study highlights the importance of engineering proteins along with pathways as a key strategy in achieving microbial biosynthesis and overproduction of pharmaceutical and chemical products.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Effendi
authors.initials: E
authors.lastname: Leonard
authors.forename: Parayil Kumaran
authors.initials: PK
authors.lastname: Ajikumar
authors.forename: Kelly
authors.initials: K
authors.lastname: Thayer
authors.forename: Wen-Hai
authors.initials: WH
authors.lastname: Xiao
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Mo
authors.forename: Bruce
authors.initials: B
authors.lastname: Tidor
authors.forename: Gregory
authors.initials: G
authors.lastname: Stephanopoulos
authors.forename: Kristala L J
authors.initials: KL
authors.lastname: Prather
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D051231:Farnesyltranstransferase / Q000235:genetics / Q000378:metabolism*; D045782:Hemiterpenes / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism; D015202:Protein Engineering; D013729:Terpenes / Q000378:metabolism*
chemical_list: D045782:Hemiterpenes; D009943:Organophosphorus Compounds; D013729:Terpenes; C004809:isopentenyl pyrophosphate; C043060:3,3-dimethylallyl pyrophosphate; D019883:Alkyl and Aryl Transferases; C434663:levopimaradiene synthase; D051231:Farnesyltranstransferase