One-Pot Conversion of L-Threonine into L-Homoalanine: Biocatalytic Production of an Unnatural Amino Acid from a Natural One
✍ Scribed by Eulsoo Park; Minji Kim; Jong-Shik Shin
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 259 KB
- Volume
- 352
- Category
- Article
- ISSN
- 1615-4150
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✦ Synopsis
A novel biocatalytic process for production of l-homoalanine from l-threonine has been developed using coupled enzyme reactions consisting of a threonine deaminase (TD) and an w-transaminase (w-TA). TD catalyzes the dehydration/deamination of l-threonine, leading to the generation of 2-oxobutyrate which is asymmetrically converted to l-homoalanine via transamination with benzylA C H T U N G T R E N N U N G amine executed by w-TA. To make up the coupled reaction system, we cloned and overexpressed a TD from Escherichia coli and an (S)-specific w-TA from Paracoccus denitrificans. In the coupled reactions, lthreonine serves as a precursor of 2-oxobutyrate for the w-TA reaction, eliminating the need for employing the expensive oxo acid as a starting reactant. In contrast to a-transaminase reactions in which use of amino acids as an exclusive amino donor limits complete conversion, amines are exploited in the w-TA reaction and thus maximum conversion could reach 100%. The w-TA-only reaction with 10 mM 2-oxobutyrate and 20 mM benzylamine resulted in 94% yield of optically pure l-homoalanine (ee > 99%). However, the w-TA-only reaction did not produce any detectable amount of l-homoalanine from 10 mM lthreonine and 20 mM benzylamine, whereas the w-TA reaction coupled with TD led to 91% conversion of l-threonine to l-homoalanine.