Sterile alpha and toll/interleukin receptor (TIR) motif-containing protein 1 (SARM1) plays a pivotal role in triggering the neurodegenerative processes that underlie peripheral neuropathies, traumatic brain injury, and neurodegenerative diseases. Importantly, SARM1 knockdown or knockout prevents degeneration, thereby demonstrating that SARM1 is a promising therapeutic target. Recently, SARM1 was shown to promote neurodegeneration via its ability to hydrolyze NAD+, forming nicotinamide and ADP ribose (ADPR). Herein, we describe the initial kinetic characterization of full-length SARM1, as well as the truncated constructs corresponding to the SAM1-2TIR and TIR domains, highlighting the distinct challenges that have complicated efforts to characterize this enzyme. Moreover, we show that bacterially expressed full-length SARM1 (kcat/KM = 6000 ± 2000 M-1 s-1) is at least as active as the TIR domain alone (kcat/KM = 1500 ± 300 M-1 s-1). Finally, we show that the SARM1 hydrolyzes NAD+ via an ordered uni-bi reaction in which nicotinamide is released prior to ADPR.

中文翻译：

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无菌 Alpha 和 Toll/白细胞介素受体基序的含蛋白质 1 的初始动力学表征。

无菌 α 和 toll/白细胞介素受体 (TIR) 基序蛋白 1 (SARM1) 在触发周围神经病变、创伤性脑损伤和神经退行性疾病的神经退行性过程中起关键作用。重要的是，SARM1 敲低或敲除可防止退化，从而证明 SARM1 是一个有前途的治疗靶点。最近，SARM1 被证明通过其水解 NAD+ 的能力促进神经退行性变，形成烟酰胺和 ADP 核糖 (ADPR)。在这里，我们描述了全长 SARM1 的初始动力学特征，以及对应于 SAM1-2TIR 和 TIR 结构域的截短结构，强调了表征这种酶的复杂努力的不同挑战。而且，我们表明，细菌表达的全长 SARM1 (kcat/KM = 6000 ± 2000 M-1 s-1) 至少与单独的 TIR 域一样活跃 (kcat/KM = 1500 ± 300 M-1 s-1)。最后，我们表明 SARM1 通过有序的单双反应水解 NAD+，其中烟酰胺在 ADPR 之前释放。