NAD(+) hydrolase, which plays a key role in axonal degeneration following injury by regulating NAD(+) metabolism (PubMed:25908823, PubMed:27671644, PubMed:28334607). Acts as a negative regulator of MYD88- and TRIF-dependent toll-like receptor signaling pathway by promoting Wallerian degeneration, an injury-induced form of programmed subcellular death which involves degeneration of an axon distal to the injury site (PubMed:15123841, PubMed:16964262, PubMed:20306472, PubMed:25908823). Wallerian degeneration is triggered by NAD(+) depletion: in response to injury, SARM1 is activated and catalyzes cleavage of NAD(+) into ADP-D-ribose (ADPR), cyclic ADPR (cADPR) and nicotinamide; NAD(+) cleavage promoting cytoskeletal degradation and axon destruction (PubMed:25908823, PubMed:28334607, PubMed:30333228, PubMed:31128467, PubMed:31439793, PubMed:32049506, PubMed:32828421, PubMed:31439792, PubMed:33053563). Also able to hydrolyze NADP(+), but not other NAD(+)-related molecules (PubMed:29395922). Can activate neuronal cell death in response to stress (PubMed:20306472). Regulates dendritic arborization through the MAPK4-JNK pathway (By similarity). Involved in innate immune response: inhibits both TICAM1/TRIF- and MYD88-dependent activation of JUN/AP-1, TRIF-dependent activation of NF-kappa-B and IRF3, and the phosphorylation of MAPK14/p38 (PubMed:16964262). H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide NAD(+) = cyclic ADP-ribose + H(+) + nicotinamide H2O + NADP(+) = ADP-D-ribose 2'-phosphate + H(+) + nicotinamide Autoinhibited: in the inactive state, the enzymatic TIR domain is held apart by the autoinhibiting ARM repeats (PubMed:27671644, PubMed:31278906, PubMed:32755591, PubMed:33053563). NAD(+)-binding to ARM repeats maintains an inactive state by promoting interaction between ARM repeats and the TIR domain, thereby facilitating inhibition of the enzymatic TIR domain (PubMed:33053563). Following activation, possibly by nicotinamide mononucleotide (NMN), auto-inhibitory interactions are released, allowing self-association of the TIR domains and subsequent activation of the NAD(+) hydrolase (NADase) activity (PubMed:27671644, PubMed:31128467, PubMed:32755591). Self-association of TIR domains is facilitated by the octamer of SAM domains (PubMed:31278906, PubMed:31439792). NAD(+) hydrolase activity is inhibited by nicotinamide (PubMed:28334607). Specifically inhibited by berberine chloride and zinc chloride (PubMed:32828421). kcat is 10.3 min(-1) with NAD(+) as substrate. Homooctamer; forms an octomeric ring via SAM domains (PubMed:31278906, PubMed:31439792, PubMed:32755591, PubMed:33053563). Interacts with TICAM1/TRIF and thereby interferes with TICAM1/TRIF function (PubMed:16964262). Interacts with MAPK10/JNK3 and SDC2 (via cytoplasmic domain) (By similarity). Associated with microtubules. Predominantly expressed in brain, kidney and liver. Expressed at lower level in placenta. Up-regulated by lipopolysaccharides (LPS). The TIR domain mediates NAD(+) hydrolase (NADase) activity (PubMed:28334607). Self-association of TIR domains is required for NADase activity (PubMed:27671644, PubMed:31278906). The ARM repeats inhibit the NAD(+) hydrolase (NADase) activity by binding to NAD(+): NAD(+)-binding to ARM repeats facilitates inhibition of the TIR domain NADase through their domain interface (PubMed:33053563). In contrast to classical ARM repeats, the last helix of ARM 6 does not fold back to interact with the first two helices, but instead turns towards the N-terminus of SARM1 (PubMed:33053563). As a result, the two following motifs ARM 7 and ARM 8 reverse their directions and lie perpendicularly (PubMed:33053563). Moreover, ARM repeats interact with different domains not only within each protomer but also of the adjacent ones (PubMed:33053563). Phosphorylation at Ser-548 by JNK kinases (MAPK8, MAPK9 and /or MAPK10) enhance the NAD(+) hydrolase (NADase) activity (PubMed:30333228). Phosphorylation at Ser-548 and subsequent activation takes place in response to oxidative stress conditions and inhibits mitochondrial respiration (PubMed:30333228). Belongs to the SARM1 family.