Sphingomyelinase is an enzyme that breaks down sphingomyelin, a type of lipid found in cell membranes. It plays a crucial role in the metabolism of sphingolipids, which are important for cell signaling and membrane structure. There are two main types of sphingomyelinase: acid sphingomyelinase, which functions optimally in acidic environments, and neutral sphingomyelinase, which works best at neutral pH levels. The activity of sphingomyelinase is essential for various biological processes, including apoptosis (programmed cell death) and inflammation. Dysregulation of this enzyme can lead to several health issues, including Niemann-Pick disease, a genetic disorder that affects lipid metabolism and can cause severe neurological symptoms.