In 2000, an N-SMase protein was partially purified from bovine brain and reported as a magnesium-dependent, membrane-bound N-SMase (Bernardo et al., 2000). Subsequently, peptide sequences from the bovine brain N-SMase facilitated the identification of the third mammalian N-SMase protein, termed nSMase3 (Krut et al., 2006). The gene for nSMase3 is localized to human chromosome 2q21.1 and encodes a protein of 866 amino acids with predicted molecular mass of 97.8 kDa. Surprisingly, the amino acid sequence of nSMase3 possessed very low homology to the previously cloned nSMase1 and nSMase2. Indeed, nSMase3 was reported to be relatively highly conserved from higher to lower animals (Krut et al., 2006), suggesting it may form a distinct N-SMase family in its own right. Importantly, nSMase3 was reported to possess both in vitro and in vivo N-SMase activity, being reported to modulate sphingolipid levels when transiently or stably expressed (Corcoran et al., 2008; Krut et al., 2006). The nSMase3 protein is a C-tail-anchored integral membrane protein containing an ER signal in the C-terminus and a proline-rich region at the N-terminus, which could potentially mediate protein-protein interactions
