Asymmetric synthesis of lipitor chiral intermediate using a robust carbonyl reductase at high substrate to catalyst ratio

• RpCR shares low sequence identity with known COBE carbonyl reductases.
• RpCR exhibits a high kcat/Km of 1747 s−1 mM−1.
• The substrate to catalyst ratio and space-time yield of RpCR reached 70 and 1480 g L−1 d−1.

An NADPH-dependent carbonyl reductase (RpCR) from Rhodococcus pyridinivorans was discovered by genome mining for the asymmetric reduction of ethyl 4-chloro-3-oxo-butanoate (COBE). RpCR has been soluble expressed in Escherichia coli BL21(DE3). The highest activity is determined at pH 5.0 and 50 °C toward COBE. The apparent Km and kcat/Km are 0.39 mM and 1747 s−1 mM−1, endowing RpCR with high catalytic efficiency in reduction of COBE. Employing merely 0.1 g recombinant RpCR-GDH in a toluene-aqueous biphasic system, as much as 7.0 g COBE could be asymmetrically reduced into ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE] (>99% ee) without addition of external cofactor, achieving molar isolation yield of 91%, substrate to biocatalyst ratio of 70 and space-time yield of 1480 g L−1 d−1. Our results indicate the robust RpCR could be potentially applied in the preparation of optically pure (S)-CHBE.

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