Single Amino Acid Substitution in Bacillus sphaericus Phenylalanine Dehydrogenase Dramatically Increases Its Discrimination between Phenylalanine and Tyrosine Substrates

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Why is it important?

Our protein engineering of PheDH was based on homology modelling guided by the GluDH structure. Unusually for a PheDH ours showed similar activity with Tyr and Phe. The homology model suggested this must be due to Asn 145, non-polar in most other PheDHs. Mutation to Ala/Val/Leu/Ile introduced a strong discrimination in favour of Phe, validating the model and helping to make an enzyme suitable for PKU diagnostics.