The mechanism by which molecular oxygen is activated by the organic cofactor pyridoxal phosphate (PLP) for oxidation reactions remains poorly understood. Recent work has identified arginine oxidases that catalyze desaturation or hydroxylation reactions. Here, we investigate a desaturase from the Pseudoalteromonas luteoviolacea indolmycin pathway. Our work, combining X-ray crystallographic, biochemical, spectroscopic, and computational studies, supports a shared mechanism with arginine hydroxylases, involving two rounds of single-electron transfer to oxygen and superoxide rebound at the 4′ carbon of the PLP cofactor. The precise positioning of a water molecule in the active site is proposed to control the final reaction outcome. This proposed mechanism provides a unified framework to understand how oxygen can be activated by PLP-dependent enzymes for oxidation of arginine and elucidates a shared mechanistic pathway and intertwined evolutionary history for arginine desaturases and hydroxylases.

分子氧被有机辅因子磷酸吡哆醛 (PLP) 激活以进行氧化反应的机制仍然知之甚少。最近的工作已经确定了催化去饱和或羟基化反应的精氨酸氧化酶。在这里，我们研究了来自Pseudoalteromonas luteoviolacea的去饱和酶吲哚霉素途径。我们的工作结合了 X 射线晶体学、生化、光谱和计算研究，支持与精氨酸羟化酶的共同机制，包括两轮单电子转移到氧气和 PLP 辅因子 4' 碳处的超氧化物反弹。提出了在活性位点中精确定位水分子以控制最终反应结果。这种提出的机制提供了一个统一的框架来理解氧如何被 PLP 依赖性酶激活以氧化精氨酸，并阐明了精氨酸去饱和酶和羟化酶的共同机制途径和相互交织的进化历史。