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Adv Synth Catal. 2017 Jun 19;359(12):2109-2120. doi: 10.1002/adsc.201700428. Epub 2017 May 19.

A Methylidene Group in the Phosphonic Acid Analogue of Phenylalanine Reverses the Enantiopreference of Binding to Phenylalanine Ammonia-Lyases.

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Department of Organic Chemistry and Technology Budapest University of Technology and Economics Műegyetem rkp. 3. H-1111 Budapest Hungary.
Institute of Enzymology HAS-Research Center of Natural Sciences, Budapest, H-1117 Magyar tudósok krt. 2. Budapest Hungary.
Institute of Organic Chemistry University of Vienna Währinger Str. 38 1090 Vienna Austria.
Institute of Inorganic Chemistry University of Vienna Währinger Str. 42. A-1090 Vienna Austria.
Institute of Pharmaceutical Sciences Pharmaceutical (Bio-)Analysis Eberhard-Karls-University Tübingen Auf der Morgensstelle 872076 Tübingen Germany.
Biocatalysis and Biotransformation Research Centre Faculty of Chemistry and Chemical Engineering Babeş-Bolyai University of Cluj-Napoca Arany János Str. 11400028 Cluj-Napoca Romania.
Department of Applied Biotechnology and Food Science Budapest University of Technology and Economics Műegyetem rkp. 3. H-1111 Budapest Hungary.


Aromatic amino acid ammonia-lyases and aromatic amino acid 2,3-aminomutases contain the post-translationally formed prosthetic 3,5-dihydro-4-methylidene-5H-imidazol-5-one (MIO) group. MIO enzymes catalyze the stereoselective synthesis of α- or β-amino acid enantiomers, making these chemical processes environmentally friendly and affordable. Characterization of novel inhibitors enables structural understanding of enzyme mechanism and recognizes promising herbicide candidates as well. The present study found that both enantiomers of the aminophosphonic acid analogue of the natural substrate phenylalanine and a novel derivative bearing a methylidene at the β-position inhibited phenylalanine ammonia-lyases (PAL), representing MIO enzymes. X-ray methods unambiguously determined the absolute configuration of all tested enantiomers during their synthesis. Enzyme kinetic measurements revealed the enantiomer of the methylidene-substituted substrate analogue as being a mirror image relation to the natural l-phenylalanine as the strongest inhibitor. Isothermal titration calorimetry (ITC) confirmed the binding constants and provided a detailed analysis of the thermodynamic driving forces of ligand binding. Molecular docking suggested that binding of the (R)- and (S)-enantiomers is possible by a mirror image packing.


MIO enzymes; amino acids; aminophosphonic acids; bioinformatics; calorimetry; enzyme inhibition

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