Acid sphingomyelinase is one of the enzymes that make up the sphingomyelinase (SMase) family, responsible for catalyzing the breakdown of sphingomyelin to ceramide and phosphorylcholine. They are organized into alkaline, neutral, and acidic SMase depending on the pH in which their enzymatic activity is optimal. Acid Sphingomyelinases (aSMases) enzymatic activity can be influenced by lipids, cations, pH, redox and other proteins in the environment. Specifically aSMases have been shown to have increased enzymatic activity in lysobisphophatidic acid (LBPA) or phosphatidylinositol (PI) enriched environments, and inhibited activity when phosphorylated derivatives of PI are present. Acid sphingomyelinase is one of the enzymes that make up the sphingomyelinase (SMase) family, responsible for catalyzing the breakdown of sphingomyelin to ceramide and phosphorylcholine. They are organized into alkaline, neutral, and acidic SMase depending on the pH in which their enzymatic activity is optimal. Acid Sphingomyelinases (aSMases) enzymatic activity can be influenced by lipids, cations, pH, redox and other proteins in the environment. Specifically aSMases have been shown to have increased enzymatic activity in lysobisphophatidic acid (LBPA) or phosphatidylinositol (PI) enriched environments, and inhibited activity when phosphorylated derivatives of PI are present. Sphingomyelin phosphodiesterase 1 is the gene that codes for two aSMase enzymes distinct in the pools of Sphingomyelin they hydrolyse. Lysosomal sphingomyelinase (L-SMase) is found in the lysosomal compartment, and the secretory sphingomyelinase (S-SMase) is found extracellularly.