Department of Biological Sciences, University of California, Santa Barbara, California 93106.
Plant Physiol. 1972 May;49(5):716-21. doi: 10.1104/pp.49.5.716.
Previous work in this laboratory has shown that cucumber (Cucumis sativus L.) seedlings contain large amounts, relative to other indolic compounds, of extractable indole-3-ethanol (IEt); tracer studies have established that IEt is metabolized to IAA. We have now succeeded in isolating an enzyme from these seedlings which catalyzes the oxidation of IEt to indole-3-acetaldehyde (IAAld). The identification of the product as IAAld was based on solvent partitioning of the free aldehyde and its bisulfite adduct and radiochromatography following incubation of enzyme with (14)C-IEt. A novel, quantitative colorimetric test for IAAld was also developed utilizing the Salkowski reagent. Partial purification of the enzyme was achieved by salt gradient chromatography on Bio-Rex 70, heating the preparation to 70 C, and chromatography on Sephadex G-150. This purification procedure yielded an enzyme activity purified in excess of 3000-fold, and studies on a standardized Sephadex column suggest a molecular weight of the enzyme of approximately 105,000. The reaction was found to proceed only aerobically; and, in the absence of other electron acceptors, O(2) appears to be reduced to H(2)O(2). The enzyme has nearly maximum activity from pH 8 to 11.
先前在本实验室的工作表明，相对于其他吲哚类化合物，黄瓜（Cucumis sativus L.）幼苗中含有大量可提取的吲哚-3-乙醇（IEt）；示踪研究已经确定 IEt 被代谢为 IAA。我们现在已经成功地从这些幼苗中分离出一种酶，它可以催化 IEt 氧化为吲哚-3-乙醛（IAAld）。产物被鉴定为 IAAld 的依据是游离醛及其亚硫酸氢盐加合物的溶剂分配以及在（14）C-IEt 孵育后酶的放射色谱分析。还利用 Salkowski 试剂开发了一种新型的、定量比色法测定 IAAld 的方法。通过在 Bio-Rex 70 上进行盐梯度层析、将制剂加热至 70°C 以及在 Sephadex G-150 上进行层析，实现了酶的部分纯化。该纯化程序使酶的活性得到了超过 3000 倍的纯化，并且在标准化的 Sephadex 柱上的研究表明该酶的分子量约为 105,000。该反应仅在有氧条件下进行；并且，在没有其他电子受体的情况下，O(2) 似乎被还原为 H(2)O(2)。该酶在 pH 8 到 11 之间具有几乎最大的活性。
