Abt. Schell, Max-Planck-Institut für Züchtungsforschung, D-5000, Köln 30.
Planta. 1985 Feb;163(2):257-62. doi: 10.1007/BF00393516.
The T-region of Ti plasmids expresses two genes (No. 1 and 2) in crown-gall cells which are essential for auxin effects. It has been shown that gene 2 (=IaaH) codes for an amidohydrolase which converts indole-3-acetamide into indole-3-acetic acid and which is functional in bacteria and in crown-gall cells (Schröder et al. (1984), Eur. J. Biochem. 138, 387-391). In this report we describe a quantitative assay for the enzyme and its application to analyze the properties of the enzyme as expressed in plant cells and in Escherichia coli. The enzyme requires no cofactors, and the temperature optimum (30-37°C), pH optimum (8.5-9.5), and Km (about 1 μM) were very similar in both systems. Besides indole-3-acetamide, the enzyme also hydrolyzed indole-3-acetonitrile, esters of indole-3-acetic acid with glucose and myo-inositol, a-naphthaleneacetamide, and phenylacetamide, indicating that it may have a general function in converting substances of low auxin activity into those with high auxin activity. The results are discussed in relation to the possible function of T-DNA gene 1 which cooperates with gene 2 in evoking auxin effects in crown-gall cells.
Ti 质粒的 T 区在冠瘿细胞中表达两个基因（1 号和 2 号），它们对生长素的作用是必需的。已经表明，2 号基因（=IaaH）编码一种酰胺水解酶，它将吲哚-3-乙酰胺转化为吲哚-3-乙酸，并且在细菌和冠瘿细胞中都具有功能（Schröder 等人，（1984），Eur. J. Biochem. 138, 387-391）。在本报告中，我们描述了一种用于该酶的定量测定法，并将其应用于分析该酶在植物细胞和大肠杆菌中表达的特性。该酶不需要辅助因子，其最适温度（30-37°C）、最适 pH（8.5-9.5）和 Km（约 1 μM）在这两个系统中非常相似。除了吲哚-3-乙酰胺，该酶还水解吲哚-3-乙腈、吲哚-3-乙酸与葡萄糖和肌醇的酯、a-萘乙酰胺和苯乙酰胺，表明它可能具有将低生长素活性的物质转化为高生长素活性物质的一般功能。讨论结果与 T-DNA 基因 1 的可能功能有关，该基因与基因 2 合作在冠瘿细胞中引发生长素作用。
