Radical SAM enzymes use S-adenosyl-L-methionine as an oxidant to initiate radical-mediated transformations that would otherwise not be possible with Lewis acid/base chemistry alone. These reactions are either redox neutral or oxidative leading to certain expectations regarding the role of SAM as either a reusable cofactor or the ultimate electron acceptor during each turnover. However, these expectations are frequently not realized resulting in fundamental questions regarding the redox handling and movement of electrons associated with these biological catalysts. Herein we provide a focused perspective on several of these questions and associated hypotheses with an emphasis on recently discovered radical SAM enzymes.

中文翻译：

---

跟随电子：自由基SAM酶催化循环的特殊性

自由基SAM酶使用S-腺苷-L-蛋氨酸作为氧化剂来引发自由基介导的转化，而单独使用路易斯酸/碱化学方法则无法实现。这些反应是氧化还原中性的或氧化性的，导致对每次转换过程中SAM作为可重复使用的辅因子或最终电子受体的作用有一定的期望。然而，这些期望经常没有被实现，从而导致了关于与这些生物催化剂相关的氧化还原处理和电子移动的根本问题。在本文中，我们将重点介绍这些问题中的几个以及相关的假设，重点是最近发现的自由基SAM酶。