Department of Applied Biological Chemistry, Faculty of Agriculture, and Graduate School of Science and Technology, Niigata University, Ikarashi 2-8050, Nishi-ku, Niigata, 950-2181, Japan.
Appl Microbiol Biotechnol. 2011 Sep;91(6):1463-75. doi: 10.1007/s00253-011-3468-z. Epub 2011 Jul 22.
Violacein is a natural violet pigment produced by several gram-negative bacteria, including Chromobacterium violaceum, Janthinobacterium lividum, and Pseudoalteromonas tunicata D2, among others. This pigment has potential medical applications as antibacterial, anti-trypanocidal, anti-ulcerogenic, and anticancer drugs. The structure of violacein consists of three units: a 5-hydroxyindole, an oxindole, and a 2-pyrrolidone. The biosynthetic origins of hydrogen, nitrogen, and carbon in the pyrrolidone nucleus were established by feeding experiments using various stable isotopically labeled tryptophans (Trps). Pro-S hydrogen of CH(2) at the 3-position of Trp is retained during biosynthesis. The nitrogen atom is exclusively from the α-amino group, and the skeletal carbon atoms originate from the side chains of the two Trp molecules. All three oxygen atoms in the violacein core are derived from molecular oxygen. The most interesting biosynthetic mechanism is the 1,2-shift of the indole nucleus on the left side of the violacein scaffold. The alternative Trp molecule is directly incorporated into the right side of the violacein core. This indole shift has been observed only in violacein biosynthesis, despite the large number of natural products having been isolated. There were remarkable advances in biosynthetic studies in 2006-2008. During the 3 years, most of the intermediates and the complete pathway were established. Two independent processes are involved: the enzymatic process catalyzed by the five proteins VioABCDE or the alternative nonenzymatic oxidative decarboxylation reactions. The X-ray crystallographic structure of VioE that mediates the indole rearrangement reaction was recently identified, and the mechanism of the indole shift is discussed here.
紫色素是由几种革兰氏阴性细菌产生的天然紫色色素，包括紫色杆菌、紫色游动放线菌和假交替单胞菌 D2 等。这种色素具有作为抗菌、抗锥虫、抗溃疡和抗癌药物的潜在医学应用。紫色素的结构由三个单元组成：5-羟基吲哚、吲哚和 2-吡咯烷酮。使用各种稳定同位素标记色氨酸（Trps）的喂养实验确定了吡咯烷酮核中氢、氮和碳的生物合成来源。Trp 第 3 位的 CH(2)的 Pro-S 氢在生物合成过程中被保留。氮原子仅来自α-氨基，骨架碳原子源自两个 Trp 分子的侧链。紫色素核心的所有三个氧原子均来自分子氧。最有趣的生物合成机制是吲哚核在紫色素支架的左侧 1,2-移位。替代的 Trp 分子直接掺入紫色素核心的右侧。尽管已经分离出了大量的天然产物，但这种吲哚移位仅在紫色素生物合成中观察到。2006-2008 年，在生物合成研究方面取得了显著进展。在这 3 年中，建立了大多数中间体和完整途径。涉及两个独立的过程：由 VioABCDE 五个蛋白催化的酶促过程或替代的非酶促氧化脱羧反应。介导吲哚重排反应的 VioE 的 X 射线晶体结构最近被确定，并且在此讨论了吲哚移位的机制。
