Paulomycins (PAUs) refer to a group of glycosylated antibiotics with attractive antibacterial activities against Gram-positive bacteria. They contain a special ring A moiety that is prone to dehydrate between C-4 and C-5 to a quinone-type form at acidic condition, which will reduce the antibacterial activities of PAUs significantly. Elucidation of the biosynthetic mechanism of the ring A moiety may facilitate its structure modifications by combinatorial biosynthesis to generate PAU analogues with enhanced bioactivity or stability. Previous studies showed that the ring A moiety is derived from chorismate, which is converted to 3-hydroxyanthranilic acid (3-HAA) by a 2-amino-2-deoxyisochorismate (ADIC) synthase, a 2,3-dihydro-3-hydroxyanthranilic acid (DHHA) synthase, and a DHHA dehydrogenase. Unfortunately, little is known about the conversion process from 3-HAA to the highly decorated ring A moiety of PAUs. In this work, we characterized Pau17 as an unprecedented 3-HAA 6-hydroxylase responsible for the conversion of 3-HAA to 3,6-DHAA by in vivo and in vitro studies, pushing one step forward toward elucidating the biosynthetic mechanism of the ring A moiety of PAUs.

保霉素（PAU）是指一组对革兰氏阳性菌具有有吸引力的抗菌活性的糖基化抗生素。它们含有一个特殊的环 A 部分，在酸性条件下，C-4 和 C-5 之间容易脱水成醌型形式，这将显着降低 PAU 的抗菌活性。阐明环 A 部分的生物合成机制可以通过组合生物合成促进其结构修饰，以产生具有增强生物活性或稳定性的 PAU 类似物。先前的研究表明，环 A 部分源自分支酸，后者通过 2-氨基-2-脱氧异分支酸 (ADIC) 合酶（一种 2,3-二氢-3-羟基邻氨基苯甲酸）转化为 3-羟基邻氨基苯甲酸 (3-HAA)酸 (DHHA) 合酶和 DHHA 脱氢酶。很遗憾，关于从 3-HAA 到高度装饰的 PAU 环 A 部分的转化过程知之甚少。在这项工作中，我们将 Pau17 表征为一种前所未有的 3-HAA 6-羟化酶，负责通过以下方式将 3-HAA 转化为 3,6-DHAA体内和体外研究，在阐明 PAU 环 A 部分的生物合成机制方面向前迈进了一步。