Tzin Vered, Galili Gad
Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100 Israel.
Arabidopsis Book. 2010;8:e0132. doi: 10.1199/tab.0132. Epub 2010 May 17.
The aromatic amino acids phenylalanine, tyrosine and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursors for a wide range of secondary metabolites that are important for plant growth as well as for human nutrition and health. The aromatic amino acids are synthesized via the shikimate pathway followed by the branched aromatic amino acid metabolic pathway, with chorismate serving as a major branch point intermediate metabolite. Yet, the regulation of their synthesis is still far from being understood. So far, only three enzymes in this pathway, namely, chorismate mutase of phenylalanine and tyrosine synthesis, tryptophan synthase of tryptophan biosynthesis and arogenate dehydratase of phenylalanine biosynthesis, proved experimentally to be allosterically regulated. The major biosynthesis route of phenylalanine in plants occurs via arogenate. Yet, recent studies suggest that an alternative route of phynylalanine biosynthesis via phenylpyruvate may also exist in plants, similarly to many microorganisms. Several transcription factors regulating the expression of genes encoding enzymes of both the shikimate pathway and aromatic amino acid metabolism have also been recently identified in Arabidopsis and other plant species.
植物中的芳香族氨基酸苯丙氨酸、酪氨酸和色氨酸不仅是蛋白质合成的必需成分，也是多种次生代谢产物的前体，这些次生代谢产物对植物生长以及人类营养与健康都很重要。芳香族氨基酸通过莽草酸途径合成，随后进入分支的芳香族氨基酸代谢途径，分支酸是主要的分支点中间代谢产物。然而，它们合成的调控机制仍远未被理解。到目前为止，该途径中只有三种酶，即苯丙氨酸和酪氨酸合成中的分支酸变位酶、色氨酸生物合成中的色氨酸合酶以及苯丙氨酸生物合成中的预苯酸脱水酶，被实验证明受到别构调节。植物中苯丙氨酸的主要生物合成途径是通过预苯酸。然而，最近的研究表明，植物中可能也存在一条类似许多微生物的、通过苯丙酮酸合成苯丙氨酸的替代途径。最近在拟南芥和其他植物物种中还鉴定出了几种调控莽草酸途径和芳香族氨基酸代谢中酶编码基因表达的转录因子。
