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Production of aromatic d-amino acids from α-keto acids and ammonia by coupling of four enzyme reactions

1999; Elsevier BV; Volume: 6; Issue: 3 Linguagem: Inglês

10.1016/s1381-1177(98)00073-3

1873-3158

Hee-Sung Bae, Seung‐Goo Lee, Seung-Pyo Hong, Mi‐Sun Kwak, Nobuyoshi Esaki, Kenji Soda, Moon‐Hee Sung,

Polyamine Metabolism and Applications

A multi-enzyme system composed of glutamate racemase, thermostable d-amino acid aminotransferase, glutamate dehydrogenase and formate dehydrogenase was employed for the production of aromatic d-amino acids, d-phenylalanine and d-tyrosine, from the corresponding α-keto acids, phenylpyruvate and hydroxyphenylpyruvate, respectively. The optimal concentration of ammonium formate for the production of these d-amino acids was found in the range of 0.25–1.0 M. The optimal concentration of α-keto acid was determined to be 50 mM, above which the productivity greatly decreased. To keep the concentration of α-keto acid around this concentration, α-keto acid was intermittently fed into the multi-enzyme system during the production period. By running the multi-enzyme system for 35 h, 48 g l−1 of d-phenylalanine and 60 g l−1 of d-tyrosine were produced with 100% of optical purity from the equimolar amounts of phenylpyruvate and hydroxyphenylpyruvate, respectively. The production levels of both aromatic d-amino acids were demonstrated to be dependent on the stability of glutamate racemase.