Protein Engineering by Rational Enzyme Design

An aromahc L-amino acid transaminase from Enterobacter sp. with unknown structure and no substrate specificity toward aromahc amino acid analogs was used to synthesize the L-phenylalanine analog L-diphenylalanine. Based on the interaction of fhe substrafe wifh the achve site of fhe enzyme, sife-directed mutagenesis can alter the substrate specificity of the transaminase toward substrates with bulky side chains [118]. 

To change the enanhopreference of transaminases, Hohne et al. searched in silico databases and took a closer look at o-selechve and branched-chain transaminases [26]. After cloning the synthehc genes the new enzymes were investigated for selective activity and desired enanhopreference. The ee of the newly identified (R)-selective transaminase was 99.6%, and its achvity was found to be in the same range as the known (S)-selechve hansaminase, which makes it suitable for the asymmetric synthesis of (R)-amines. 

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