在水/有机两相中将羰基还原酶SyS1、葡萄糖1-脱氢酶SyGDH和卤代醇脱卤酶CSyHheC偶联催化α-溴代苯乙酮以高效制备(S)-环氧苯乙烷(SO)。第1步反应催化α-溴代苯乙酮不对称还原为(S)-2-溴-1-苯基乙醇((S)-BPE)及NADPH的原位再生,其优化的反应条件:100 mmol/L磷酸钾缓冲液(p H 8.0)/正己烷(V∶V=4∶6)、40 mmol/Lα-溴代苯乙酮、80 mmol/LD-葡萄糖、0.2 mmol/L NADP+和70 mg/m L E.coli/Sygdh-Sys1湿菌体(共表达SyGDH和SyS1),终体积1.0 m L,35℃反应8 h。第2步反应催化(S)-BPE脱卤闭环为(S)-SO,其反应条件:在上述反应体系中加入磷酸钾缓冲液(p H 8.0)和0.3 U SyHheC,终体积2.0 m L,35℃反应30 min。通过连续2步酶催化反应,终产物(S)-SO的摩尔产率为99%、对映体过量值〉99%。
In an aqueous/organic two-phase,cascade catalysis was carried out for the efficient preparation of(S)-styrene oxide(SO) by a combination of carbonyl reductase(SyS1),glucose 1-dehydrogenase(SyGDH) and halohydrin dehalogenase C(SyHheC). The firststep was to asymmetrically reduceα-bromoacetophenone into(S)-2-bromo-1-phenylethanol((S)-BPE) and to regenerate NADPH in situ. The optimized conditions were 100 mmol/L potassium phosphate buffer(pH 8.0)/n-hexane(v∶v=4∶6),40 mmol/L α-bromoacetophenone,80 mmol/L D-glucose,0.2 mmol/L NADP+ and 70 mg/mL wet E. coli/Sygdh-Sys1 cells(co-expressing both SyGDH and SyS1) in a volume of 1.0 mL at 35 ℃ for 8 h. The second step was dehalogenation ring-closure of(S)-BPE into(S)-SO by adding potassium phosphate buffer(pH 8.0) and 0.3 U SyHheC into the above reaction system, in a volume of 2.0 mL,at 35 ℃ for 30 min. Through two steps of enzyme catalysis,the final product(S)-SO was obtained with a molar yield of 99% and an enantiomeric excess value more than 99%.