| Title | Kinetic Study on the Enzymatic Production of D-Alanine from D-Aspartic Acid |
|---|---|
| Author | Jae-Heung Lee 1 *, Moon-Hee Sung 2 , and Yeong-Joong Jeon 3 |
| Address | 1 Department of Food and Life Science, Faculty of Life Science and Technology, Sungkyunkwan University, 300 Chunchun-dong, Jangan-gu, Suwon 440-746, K |
| Bibliography | Journal of Microbiology, 40(1),33-37, 2002, |
| DOI | |
| Key Words | D-alanine, D-amino acid aminotransferase, D-aspartic acid, competitive inhibition, ping pong mechani |
| Abstract | An enzymatic reaction for the production of D-alanine from D-aspartic acid and pyruvate as substrates by a thermostable D-amino acid aminotransferase (D-AAT) was investigated at various conditions in the temperature range of 40-70 C and pH range of 6.0-9.5. The D-AAT was produced with recombinant E. coli BL21, which hosted the chimeric plasmid pTLK2 harboring the D-AAT from the novel thermophilic Bacillus sp. LK-2. The enzyme reaction was shown to follow the Ping Pong Bi Bi mechanism. The K m values for D-aspartic acid and pyruvate were 4.38 mM and 0.72 mM, respectively. It was observed that competitive inhibition by D-alanine, the product of this reaction, was evident with the inhibition constant K i value of 0.1 mM. A unique feature of this reaction scheme is that the decarboxylation of oxaloacetic acid, one of the products, spontaneously produces pyruvate. Therefore, only a catalytic amount of pyruvate is necessary for the enzyme conversion reaction to proceed. A typical time-course kinetic study showed that D-alanine up to 88 mM could be produced from 100 mM of D-aspartic acid with a molar yield of 1.0. |
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