AbstractMupirocin is a clinically important antibiotic produced by a trans‐AT Type I polyketide synthase (PKS) in Pseudomonas fluorescens. The major bioactive metabolite, pseudomonic acid A (PA−A), is assembled on a tetrasubstituted tetrahydropyran (THP) core incorporating a 6‐hydroxy group proposed to be introduced by α‐hydroxylation of the thioester of the acyl carrier protein (ACP) bound polyketide chain. Herein, we describe an in vitro approach combining purified enzyme components, chemical synthesis, isotopic labelling, mass spectrometry and NMR in conjunction with in vivo studies leading to the first characterisation of the α‐hydroxylation bimodule of the mupirocin biosynthetic pathway. These studies reveal the precise timing of hydroxylation by MupA, substrate specificity and the ACP dependency of the enzyme components that comprise this α‐hydroxylation bimodule. Furthermore, using purified enzyme, it is shown that the MmpA KS0 shows relaxed substrate specificity, suggesting precise spatiotemporal control of in trans MupA recruitment in the context of the PKS. Finally, the detection of multiple intermodular MupA/ACP interactions suggests these bimodules may integrate MupA into their assembly.
摘要莫匹罗星(Mupirocin)是一种临床上重要的抗生素,由荧光假单胞菌(Pseudomonas fluorescens)中的反式 AT I 型多酮合成酶(PKS)产生。其主要的生物活性代谢产物假霉素 A(PA-A)是以四取代四氢吡喃(THP)为核心组装而成的,其中含有一个 6-羟基,该羟基是通过与酰基载体蛋白(ACP)结合的聚酮链硫酯的α-羟基化作用引入的。在本文中,我们介绍了一种体外方法,该方法结合了纯化酶成分、化学合成、同位素标记、质谱分析和核磁共振以及体内研究,首次确定了莫匹罗星生物合成途径中α-羟基化双模块的特征。这些研究揭示了 MupA 进行羟化的精确时间、底物特异性以及构成α-羟化双模块的酶组分对 ACP 的依赖性。此外,利用纯化的酶,研究表明 MmpA KS0 显示出宽松的底物特异性,这表明在 PKS 的背景下,对 MupA 的反式招募进行了精确的时空控制。最后,对多个模块间 MupA/ACP 相互作用的检测表明,这些双模块可能将 MupA 整合到它们的组装中。