期刊
AMINO ACIDS
卷 40, 期 1, 页码 215-220出版社
SPRINGER
DOI: 10.1007/s00726-010-0637-9
关键词
D-threo-Amino acid; Enzymatic resolution; Immobilized cells; Serine hydroxymethyl transferase
资金
- National Technology-Innovation Fund [02CJ-13-01-16]
- State Key Laboratory of Pharmaceutical Biotechnology of Nanjing University, P.R. China
In this research, an improved method for preparation of optically pure beta-hydroxy-alpha-amino acids, catalyzed by serine hydroxymethyl transferase with threonine aldolase activity, is reported. Using recombinant serine hydroxymethyl transferase (SHMT), an enzymatic resolution process was established. A series of new substrates, beta-phenylserine, beta-(nitrophenyl) serine and beta-(methylsulfonylphenyl) serine were used in the resolution process catalyzed by immobilized Escherichia coli cells with SHMT activity. It was observed that the K (m) for l-threonine was 28-fold higher than that for l-allo-threonine, suggesting that this enzyme can be classified as a low-specificity l-allo-threonine aldolase. The results also shows that SHMT activity with beta-phenylserine as substrate was about 1.48-fold and 1.25-fold higher than that with beta-(methylsulfonylphenyl) serine and beta-(nitrophenyl) serine as substrate, respectively. Reaction conditions were optimized by using 200 mmol/l beta-hydroxy-alpha-amino acid, and 0.1 g/ml of immobilized SHMT cells at pH 7.5 and 45A degrees C. Under these conditions, the immobilized cells were continuously used 10 times, yielding an average conversion rate of 60.4%. Bead activity did not change significantly the first five times they were used, and the average conversion rate during the first five instances was 84.1%. The immobilized cells exhibited favourable operational stability.
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