Screening and heterologous expression of ω-transaminase for the preparation of S-methoxyisopropylamine
An enzyme library containing 36 ω-transaminase was constructed according to the evolutionary classification of the amin-otransferase family and substrate specificity.Genes from the library were cloned into E.coli BL21(DE3)for heterologous recombinant expression of the enzymes.The enzyme expression levels were analyzed and corresponding enzyme activity and enantiomeric selectivity were determined.Through screening,the best ω-aminotransferase was found to be the one from Bacillus megaterium(Bme TA),which exhibited a crude enzyme activity of 2.0 U/mL and a pure enzyme activity of 9.5 U/mg protein.Enzymology characterization showed that the optimal temperature of Bme TA was 35℃,and the optimal pH was 8.0.Based on these,the catalytic reaction process condi-tions were further optimized,and 450 mmol/L of S-methoxyisopropylamine was obtained after an 18 h catalytic reaction under the con-ditions of 20 g/L crude enzyme and 0.5 mmol/L coenzyme dosage,and 1.4 amino donor/amino acceptor ratio,reaching a 90%con-version rate of substrate.The investigation of this study laid the foundation for the industrialization of biocatalytic preparation of S-me-thoxyisopropylamine.
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