Arogenate dehydratases: enzymes and beyond

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Phenylalanine (Phe), is one of only three amino acids that contain an aromatic ring. Phe, like other amino acids, is a building block of life as it is a basic unit for all proteins. In plants Phe also serves as a precursor to secondary or specialized metabolites including flavonoids, lignins, phenols and tannins. These specialized metabolites are essential for plants as they are required for structural support, pigmentation, scent formation, protection from UV light and predators. Arogenate dehydratases (ADTs) are catalyzing the last step in Phe biosynthesis and represent a key regulatory step for producing Phe. We are proposing a detailed molecular analysis of the six ADT genes and their six corresponding proteins in Arabidopsis, a representative model organism for plants. We predict that having that many similar but not identical enzymes allows this plant to regulate the synthesis of Phe in response to its many uses and that the ability to regulate the activity of these enzymes by internal and environmental cues is essential to the plant's ability to thrive and to survive. Regulation is a highly complex process which requires a network of actions on many molecular levels. By learning how the regulation of ADTs is accomplished, we will provide a fundamental understanding of how the various members of this ADT family contribute to the plant's survival. As Phe serves as a precursor to many specialized metabolites, understanding the role that ADTs play in aromatic amino acid synthesis can have far-reaching significance for basic and applied research. For example, if one can generally increase Phe levels in plants, these plants could be used as food with an increased nutrient value for humans and animals. Alternatively, by knowing how ADTs regulate the channeling of Phe into downstream pathways one can make plants with lower lignin content (useful if these plants are used for paper production), with increased flavonoid levels (these plants will have health benefits as flavonoids have been many beneficial properties including to anti cancer properties).