of 980 μM, a brain concentration seen in classical phenylketonuria, whereas D-phenylalanine has a significantly smaller effect. Commercial synthesis L-Phenylalanine is produced for medical, feed, and nutritional applications, such as aspartame, in large quantities by utilizing the bacterium Escherichia coli, which naturally produces aromatic amino acids like phenylalanine. The quantity of L-phenylalanine produced commercially has been increased by genetically engineering E. coli, such as by altering the regulatory promoters or amplifying the number of genes controlling enzymes responsible for the synthesis of the amino acid. Derivatives Boronophenylalanine (BPA) is a dihydroxyboryl derivative of phenylalanine, used in neutron capture therapy. 4-Azido-L-phenylalanine is a protein-incorporated unnatural amino acid used as a tool for bioconjugation in the field of chemical biology. References External links Phenylalanine mass spectrum Phenylalanine at ChemSynthesis Animal products Proteinogenic amino acids Glucogenic amino acids Ketogenic amino acids Aromatic amino acids Essential amino acids Enkephalinase inhibitors Phenyl compounds Benzyl compounds Dopamine agonists Carbonic anhydrase activators Monoamine precursors