Arogenate dehydratases: enzymes and beyond

苯丙氨酸(Phe)是仅有的三种含有芳香环的氨基酸之一。与其他氨基酸一样，苯丙氨酸是构成生命的基本单位，也是所有蛋白质的基本单位。在植物中，Phe也是次生代谢物或特殊代谢物的前体，包括类黄酮类、木质素、酚和单宁。这些专门的代谢物对植物是必不可少的，因为它们是结构支持、色素形成、气味形成、保护免受紫外线照射和捕食者所必需的。芳香酸脱水酶(ADT)是苯丙氨酸生物合成的最后一步催化剂，是苯丙氨酸合成的关键调控步骤。我们建议对拟南芥中的六个ADT基因及其相应的六个蛋白质进行详细的分子分析，拟南芥是植物的典型模式生物。我们预测，拥有如此多相似但不相同的酶使这种植物能够调节Phe的合成，以响应其多种用途，并且通过内部和环境线索调节这些酶的活性的能力对于植物的茁壮成长和生存是必不可少的。调控是一个高度复杂的过程，需要在许多分子水平上的行动网络。通过了解ADT的调控是如何完成的，我们将对ADT家族的各个成员如何对植物的生存做出贡献提供一个基本的了解。由于苯丙氨酸是许多特殊代谢物的前体，了解ADTS在芳香族氨基酸合成中的作用对于基础和应用研究具有深远的意义。例如，如果人们能够普遍提高植物中的苯丙氨酸水平，这些植物就可以被用作对人类和动物具有更高营养价值的食物。或者，通过了解ADT如何调节Phe进入下游途径，人们可以使植物的木质素含量较低(如果这些植物用于造纸)，具有更高的类黄酮水平(这些植物将对健康有益，因为类黄酮具有许多有益的特性，包括抗癌特性)。

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).