Exploiting Cell-Free Systems: Implementation and Debugging of a System of Biotransformations

The orchestration of a multitude of enzyme. catalysts allows cells to carry out complex and thermodynamically unfavorable chemical conversions. In an effort to, recruit these advantages for in vitro biotransformations, we have assembled a 10-step catalytic system-a system of biotransformations (SBT)-for the synthesis of unnatural inonosaccharides based on the versatile building block dihydroxyacetone phosphate (DHAP). To facilitate the assembly of such a network, we have insulated a production;. pathway from Escherichia coli's central carbon metabolism. This pathway consists of the endogenous glycolysis without triose-phosphate isomerase to enable accumulation of DHAP and was completed with lactate dehydrogenase to regenerate NAD(+). It could be readily extended for the synthesis of unnatural sugar molecules, such as the unnatural monosaccharide phosphate 5,6,7-trideoxy-D-threo-heptulose-1-phosphate from DHAP and butanal. Insulation required in particular inactivation of the amn gene encoding the AMP nucleosidase, which otherwise led to glucose-independent DHAP production from adenosine phosphates. The work demonstrates that a sufficiently insulated in vitro multi-step enzymatic system can be readily assembled from central carbon metabolism pathways. Biotechnol. Bioeng. 2010;106: 376-389. (C) 2010 Wiley Periodicals, Inc.