An Orthogonal and Modular Pathway for the Efficient Synthesis of Functionalized Small Molecules
Anabolic metabolism can produce an array of small molecules, but yields and productivities areÂ often limited by carbon and energy inefficiencies and slow kinetics. Catabolic and fermentativeÂ pathways, on the other hand, are carbon and energy efficient but support only a limited productÂ range. To address these limitations, we engineered an orthogonal pathway for the synthesis ofÂ functionalized small molecules based on non-decarboxylative Claisen condensation reactions (andÂ subsequent Î²-reductions) that uses functionalized primers and functionalized extender units andÂ operates in an iterative manner. This carbonâ??carbon elongation mechanism was selected because ofÂ its ability to support iterative condensation reactions at high energy (ATP) efficiency, as previouslyÂ demonstrated in our laboratory (Nature 476, 355-359, 2011). The orthogonality of the newlyÂ developed platform enables predictable, tunable, and programmable operation of a pathway thatÂ retains the high product diversity, modularity, and combinatorial capabilities of anabolism. UsingÂ different Ï?- and Ï?-1-functionalized primers and Î±-functionalized extender units in combination withÂ various termination pathways, we engineered the synthesis of 18 products from 10 classes inÂ Escherichia coli, including Ï?-phenylalkanoic, Î±,Ï?-dicarboxylic, Ï?-hydroxy, Ï?-1-oxo, Ï?-1-methyl, 2-methyl, 2-methyl-2-enolic and 2,3-dihydroxy acids, Î²-hydroxy-Ï?-lactones, and Ï?-1-methyl alcoholsÂ (Nature Biotechnology, 2016, 34 (5): 556-561.