Nucleoside triphosphates (NTPs) are important synthetic targets with diverse applications in therapeutics and diagnostics. Enzymatic routes to NTPs from simple building blocks are attractive, however the cost and complexity of assembling the requisite mixtures of multiple enzymes hinders application. Here, we describe the use of an engineered E. coli cell-free lysate as an efficient readily-prepared multi-enzyme biocatalyst for the production of uridine triphosphate (UTP) from free ribose and nucleobase. Endogenous lysate enzymes are able to support the nucleobase ribosylation and nucleotide phosphorylation steps, while uridine phosphorylation and the production of ribose phosphates (ribose 1-phosphate, ribose 5-phosphate and phosphoribosyl pyrophosphate) require recombinant enrichment of endogenous activities. Co-expression vectors encoding all required recombinant enzymes were employed for host cell transformation, such that a cell-free lysate with all necessary activities was obtained from a single bacterial culture. ATP required as phosphorylation cofactor was recycled by endogenous lysate enzymes using cheap, readily-prepared acetyl phosphate. Surprisingly, acetyl phosphate initiated spontaneous generation of ATP in the lysate, most likely from the breakdown of endogenous pools of adenosine-containing starting materials (e.g. adenosine cofactors, ribonucleic acids). The sub-stoichiometric amount of ATP produced and recycled in this way was enough to support all ATP-dependent steps without addition of any exogenous cofactor or auxiliary enzyme. Using this approach, equimolar solutions of orotic acid and ribose are transformed near quantitatively into 1.4 g L-1 UTP within 2.5 h, using a low-cost, readily-generated biocatalytic preparation.
Keywords: Cell-free lysate; Cell-free metabolic engineering; NTP; Nucleoside triphosphate; UTP; Uridine triphosphate.
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