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. Author manuscript; available in PMC: 2010 Feb 1.
Published in final edited form as: Curr Opin Chem Biol. 2009 Feb 5;13(1):35–42. doi: 10.1016/j.cbpa.2009.01.005

Figure 2.

Figure 2

Simplified schematics illustrating a few of the reactions catalyzed by megasynthase domains. A. KR domains use NADPH to reduce carbonyl groups to alcohols; exemplified here by an acetyl extender unit (malonyl group). Altering the stereoselectivity of KR domains could alter the product outcome. B. After KR and DH domain action on a propionyl extender unit (methyl-malonyl group), the resulting olefin can be reduced with NADPH by the action of stereoselective ER domains. Reengineering the ER stereoselectivity is also a potential means to alter product outcome. C. Illustration of NRPS domain actions on an amino acyl extender unit. A typical module is minimally composed of A (loading an amino acid onto the PCP domain), C (catalyzing the peptide bond formation), and PCP (carrying the amino acyl chain). The TE domain hydrolyzes the thioester linkage to release the natural product. KR: ketoreductase; DH: dehydratase; ER: enoyl-reductase; A: adenylation domain; C: condensation domain; PCP: peptidyl carrier protein domain; TE: thioesterase domain.