Nicholas J. Weise, Fabio Parmeggiani, Syed T. Ahmed, and Nicholas J. Turner*
Manchester Institute of Biotechnology
& School of Chemistry, University of
Manchester, 131 Princess
Street, M1 7DN Manchester, United Kingdom
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b07326
http://pubs.acs.org/doi/pdf/10.1021/jacs.5b07326
Abstract
Enzymes
of the class I lyase-like family catalyze the asymmetric addition of
ammonia to arylacrylates, yielding high value amino acids as products.
Recent examples include the use of phenylalanine ammonia lyases (PALs),
either alone or as a gateway to deracemization cascades (giving (S)- or (R)-α-phenylalanine derivatives, respectively), and also eukaryotic phenylalanine aminomutases (PAMs) for the synthesis of the (R)-β-products. Herein, we present the investigation of another family member, EncP from Streptomyces maritimus, thereby expanding the biocatalytic toolbox and enabling the production of the missing (S)-β-isomer. EncP was found to convert a range of arylacrylates to a mixture of (S)-α- and (S)-β-arylalanines,
with regioselectivity correlating to the strength of
electron-withdrawing/-donating groups on the ring of each substrate. The
low regioselectivity of the wild-type enzyme was addressed via
structure-based rational design to generate three variants with altered
preference for either α- or β-products. By examining various
biocatalyst/substrate combinations, it was demonstrated that the
amination pattern of the reaction could be tuned to achieve
selectivities between 99:1 and 1:99 for β:α-product ratios as desired.
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