earticle

영어

L-Homoalanine is an unnatural amino acid that is used as a building block for synthesis of pharmaceutical drugs. Here, we report an efficient biocatalytic process for production of L-homoalanine from L-threonine using coupled enzyme reactions. L-homoalanine is asymmetrically produced from 2-oxobutyrate using ω-transaminase with benzylamine as an amino donor. The expensive precursor, i.e. 2-oxobutyrate, in the transaminase reaction is produced from L-threonine through dehydration and deamination reaction using threonine deaminase. For the coupled enzyme reactions, threonine deaminase from Escherichia coli and an (S)-specific ω-transaminase from Paracoccus denitrificans were cloned and overexpressed. We performed enzyme characterization to study substrate specificity, substrate inhibition and product inhibition of the ω- transaminase form P. denitrificans. In the presence of 10 mM 2-oxobutyrate, 20 mM benzylamine and ω-transaminase, the conversion of 2-oxobutyrate into L-homoalanine was 94 % ( ee >99 % ). The coupled reaction consisting of ω-transaminase and threonine deaminase resulted in 91 % conversion of L-threonine to L-homoalanine using 10 mM L-threonine and 20 mM benzylamine. [This work was supported by the Advanced Biomass R&D Center funded by the Ministry of Education, Science and Technology (ABC-2010-0029737) and Seoul R&BD Program (KU080657).]