Genetic Engineering of Streptomyces coelicolor A3(2) for the Enantioselective Reduction of Unnatural -Keto-Ester Substrates

Abstract

Potential "reagents" for the enantioselective reduction, and other biotransformations, of beta-keto-esters result from the genetic engineering of Streptomyces coelicolor A3(2). For example, incubation of the N-acetylcysteamine thioester 1 with the recombinant strain CH999/pIJ5675 followed by treatment with MeOH/HCl gave the lactone 2 as essentially a single enantiomer.

Broad Substrate Specificity of Ketoreductases Derived from Modular Polyketide Synthases

“…A KR domain from a dissociable or type II PKS system responsible for assembling the aromatic polyketide actinorhodin has recently been shown to carry out the stereoselective reduction of β‐keto acids in whole‐cell systems 38. 39 However, in these experiments, the substrates were structurally similar to the natural polyketide intermediate.…”

Enantioselective Reduction of β‐Keto Acids with Engineered Streptomyces coelicolor

“…The fact that a range of nonnatural SNAC derivatives proved to be substrates for RED1, but that other β‐ketoesters were not, provided convincing evidence at the time for the likely existence of 2 as the thiolate (R=SEnz). These results led us to conclude that “NAC thioesters are required for recognition by the act VIORF‐1 reductase and/or they are required for successful transport across the cell membrane” 5. Herein we present results from further study that demonstrate that this statement is likely to be incorrect and that CH999/pIJ5675 is a much more general biotransformation system than previously thought.…”

Synthesis and Characterisation of Acyl Carrier Protein Bound Polyketide Analogues

“…As expected, the thiolesters 5 a – d and 5 g existed as a mixture of keto (major) and enol (minor) tautomers in CDCl 3 . We also synthesised malonyl SNAC ( 5 e )16 and acetoacetyl SNAC ( 5 f )17 by standard methods.…”