Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Saulėtekio al. 7, LT-10257 Vilnius, Lithuania.
Biomolecules. 2020 Apr 24;10(4):663. doi: 10.3390/biom10040663.
A plant auxin hormone indole-3-acetic acid (IAA) can be assimilated by bacteria as an energy and carbon source, although no degradation has been reported for indole-3-propionic acid and indole-3-butyric acid. While significant efforts have been made to decipher the Iac (indole-3-acetic acid catabolism)-mediated IAA degradation pathway, a lot of questions remain regarding the mechanisms of individual reactions, involvement of specific Iac proteins, and the overall reaction scheme. This work was aimed at providing new experimental evidence regarding the biodegradation of IAA and its derivatives. Here, it was shown that strain DSM50014 possesses a full gene cluster and is able to use IAA as a sole source of carbon and energy. Next, IacE was shown to be responsible for the conversion of 2-oxoindole-3-acetic acid (Ox-IAA) intermediate into the central intermediate 3-hydroxy-2-oxindole-3-acetic acid (DOAA) without the requirement for IacB. During this reaction, the oxygen atom incorporated into Ox-IAA was derived from water. Finally, IacA and IacE were shown to convert a wide range of indole derivatives, including indole-3-propionic acid and indole-3-butyric acid, into corresponding DOAA homologs. This work provides novel insights into Iac-mediated IAA degradation and demonstrates the versatility and substrate scope of IacA and IacE enzymes.
植物生长素激素吲哚-3-乙酸（IAA）可以被细菌作为能量和碳源同化，尽管吲哚-3-丙酸和吲哚-3-丁酸没有报道其降解。虽然已经做出了很大的努力来破译 Iac（吲哚-3-乙酸代谢）介导的 IAA 降解途径，但对于单个反应的机制、特定 Iac 蛋白的参与以及整体反应方案仍存在许多问题。这项工作旨在提供关于 IAA 及其衍生物生物降解的新的实验证据。在这里，表明菌株 DSM50014 拥有完整的基因簇，并且能够将 IAA 作为唯一的碳源和能源。接下来，表明 IacE 负责将 2-氧代吲哚-3-乙酸（Ox-IAA）中间体转化为中心中间体 3-羟基-2-氧代吲哚-3-乙酸（DOAA），而不需要 IacB。在这个反应中，Ox-IAA 中掺入的氧原子来自水。最后，表明 IacA 和 IacE 能够将广泛的吲哚衍生物，包括吲哚-3-丙酸和吲哚-3-丁酸，转化为相应的 DOAA 同系物。这项工作为 Iac 介导的 IAA 降解提供了新的见解，并展示了 IacA 和 IacE 酶的多功能性和底物范围。
