Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, USA.
DuPont Pioneer, Hayward, California, USA.
Nat Chem Biol. 2015 Jan;11(1):52-7. doi: 10.1038/nchembio.1693. Epub 2014 Nov 17.
L-Tyrosine (Tyr) and its plant-derived natural products are essential in both plants and humans. In plants, Tyr is generally assumed to be synthesized in the plastids via arogenate dehydrogenase (TyrA(a), also known also ADH), which is strictly inhibited by L-Tyr. Using phylogenetic and expression analyses, together with recombinant enzyme and endogenous activity assays, we identified prephenate dehydrogenases (TyrA(p)s, also known as PDHs) from two legumes, Glycine max (soybean) and Medicago truncatula. The identified PDHs were phylogenetically distinct from canonical plant ADH enzymes, preferred prephenate to arogenate substrate, localized outside of the plastids and were not inhibited by L-Tyr. The results provide molecular evidence for the diversification of primary metabolic Tyr pathway via an alternative cytosolic PDH pathway in plants.
L-酪氨酸（Tyr）及其植物来源的天然产物在植物和人类中都是必不可少的。在植物中，Tyr 通常被认为是在质体中通过芳香族氨基酸脱氨酶（TyrA(a)，也称为 ADH）合成的，而 ADH 受到 L-Tyr 的严格抑制。通过系统发育和表达分析，以及重组酶和内源性活性测定，我们从两种豆科植物大豆（Glycine max）和蒺藜苜蓿（Medicago truncatula）中鉴定出预苯酸脱氢酶（TyrA(p)，也称为 PDHs）。鉴定出的 PDHs 在系统发育上与典型的植物 ADH 酶不同，优先选择预苯酸作为底物，定位于质体之外，不受 L-Tyr 的抑制。这些结果为植物中通过替代的细胞质 PDH 途径使初级代谢 Tyr 途径多样化提供了分子证据。
