IAA-Synthase, an Enzyme Complex from Arabidopsis thaliana Catalyzing the Formation of Indole-3-Acetic Acid from (S)-Tryptophan
IAA-Synthase, an Enzyme Complex from Arabidopsis thaliana Catalyzing the Formation of Indole-3-Acetic Acid from (S)-Tryptophan
复制标题
IAA-合酶，一种来自拟南芥的酶复合物，催化 (S)-色氨酸形成吲哚-3-乙酸
作者：
A. Müller;E. Weiler
摘要从拟南芥中分离到一种酶复合物，它催化由（S）-色氨酸合成植物生长激素吲哚-3-乙酸（IAA）的整个途径。该160-180 kDa可溶性复合物催化严格的O2依赖性反应，无需进一步添加因子，并且对底物（S）-色氨酸具有立体特异性（约Km = 120μM）。H218 O标记证明IAA的两个氧原子都是通过H2O传递的。这一点以及复合物中腈水解酶样蛋白存在的免疫学证据表明，反应通过中间体吲哚-3-乙腈进行。IAA合成酶形成一个紧密的代谢通道，致力于IAA的生产，并存在于芽，根和细胞培养物。thaliana.
Abstract An enzyme complex was isolated from Arabidopsis thaliana that catalyzes the entire pathway of biosynthesis of the major plant growth hormone, indole-3-acetic acid (IAA), from (S)-tryptophan. The 160–180 kDa, soluble complex catalyzes a strictly O2-dependent reaction which requires no further added factors and is stereospecific for the substrate (S)-tryptophan (app. Km = 120μM). H2 18O labeling proved that both oxygen atoms of IAA were delivered via H2O. This, as well as immunological evidence for the presence of a nitrilase-like protein in the complex, suggests the reaction to proceed via the intermediate indole-3-acetonitrile. IAA-synthase forms a tight metabolite channel committed to IAA production and occurs in shoots, roots and cell cultures of A. thaliana.