Initial Kinetic Characterization of Sterile Alpha and Toll/Interleukin Receptor Motif-Containing Protein 1

Biochemistry. 2020 Mar 3;59(8):933-942. doi: 10.1021/acs.biochem.9b01078. Epub 2020 Feb 17.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Diphosphate Ribose / chemistry
  • Animals
  • Armadillo Domain Proteins / antagonists & inhibitors
  • Armadillo Domain Proteins / chemistry*
  • Armadillo Domain Proteins / isolation & purification
  • Caenorhabditis elegans / chemistry
  • Caenorhabditis elegans Proteins / chemistry
  • Cytoskeletal Proteins / antagonists & inhibitors
  • Cytoskeletal Proteins / chemistry*
  • Cytoskeletal Proteins / isolation & purification
  • Enzyme Assays
  • Enzyme Inhibitors / chemistry
  • Humans
  • Kinetics
  • Niacinamide / analogs & derivatives
  • Protein Domains
  • Receptors, G-Protein-Coupled / chemistry


  • Armadillo Domain Proteins
  • Caenorhabditis elegans Proteins
  • Cytoskeletal Proteins
  • Enzyme Inhibitors
  • Receptors, G-Protein-Coupled
  • SARM1 protein, human
  • tir-1 protein, C elegans
  • Adenosine Diphosphate Ribose
  • Niacinamide