Recombinant diketoreductase showed excellent stereoselectivity in the double reduction of β,δ-diketo esters. To investigate the substrate specificity and to broaden the applications of this new biocatalyst, a number of ketone substrates were used to evaluate the substrate spectrum and enantioselectivity of this enzyme in the present study. Among the ketone substrates tested, only this enzyme displayed high efficiency and excellent enantioselectivity in the reduction of ethyl 2-oxo-4-phenylbutyrate to ethyl (S)-2-hydroxy-4-phenylbutyrate. After optimizing the reaction conditions, the bio-reduction of ethyl 2-oxo-4-phenylbutyrate at a substrate concentration of 0.8 M (164.8 g/L) was achieved by the recombinant diketoreductase in an aqueous-toluene biphasic system coupled with formate dehydrogenase for the regeneration of cofactor, resulting in an overall hydroxyl product yield of 88.7% (99.5% ee). This new enzymatic transformation may offer a practical method for the preparation of this important chiral building block.

中文翻译：

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重组双酮还原酶的对映选择性合成（S）-2-羟基-4-苯基丁酸乙酯

重组双酮还原酶在β，δ-二酮酯的双重还原中表现出优异的立体选择性。为了研究底物特异性并拓宽这种新型生物催化剂的应用，在本研究中，许多酮底物用于评估该酶的底物光谱和对映选择性。在测试的酮底物中，只有这种酶在将2-氧代-4-苯基丁酸乙酯还原成乙基（S）-2-羟基-4-苯基丁酸酯。优化反应条件后，通过重组二酮还原酶在水-甲苯双相系统中与甲酸脱氢酶联用，可在底物浓度为0.8 M（164.8 g / L）的条件下对2-氧代-4-苯基丁酸乙酯进行生物还原。辅因子的再生，导致总羟基产物收率为88.7％（99.5％ee）。这种新的酶促转化可以为制备这种重要的手性结构单元提供实用的方法。