Choline-specific phosphodiesterase that hydrolyzes sphingomyelin (SM) releasing the ceramide and phosphocholine and therefore is involved in sphingomyelin digestion, ceramide formation, and fatty acid (FA) absorption in the gastrointestinal tract (PubMed:16255717, PubMed:15708357). Has also phospholipase C activity and can also cleave phosphocholine from palmitoyl lyso-phosphatidylcholine and platelet-activating factor (PAF) leading to its inactivation. Does not have nucleotide pyrophosphatase activity (PubMed:16255717). May promote cholesterol absorption by affecting the levels of sphingomyelin derived from either diet or endogenous sources, in the intestinal lumen (By similarity). a sphingomyelin + H2O = an N-acylsphing-4-enine + H(+) + phosphocholine a 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine + H2O = a 1-O-alkyl-2-acetyl-sn-glycerol + H(+) + phosphocholine 1-O-octadecyl-2-acetyl-sn-glycero-3-phosphocholine + H2O = 1-O-octadecyl-2-acetyl-sn-glycerol + H(+) + phosphocholine 1-hexadecanoyl-sn-glycero-3-phosphocholine + H2O = 1-hexadecanoyl-sn-glycerol + H(+) + phosphocholine platelet-activating factor hydrolysis is inhibited by higher amount of sphingomyelin (PubMed:16255717). The hydrolysis of platelet-activating factor and sphingomyelin can be inhibited by the presence of sphingomyelin and platelet-activating factor respectively, the inhibition of platelet-activating factor hydrolysis by sphingomyelin being stronger (PubMed:16255717). PAF hydrolysis is dose-dependently increased by both taurocholate (TC) and taurodeoxycholate (TDC) (PubMed:16255717). Hydrolase activity against PAF is inhibited by EDTA and stimulated by 0.1-0.25 mM Zn2+ (PubMed:16255717). Optimum pH is 7.5 (PubMed:16255717). Optimum pH is 9 (PubMed:15708357). The catalytic domain is released into the extracellular medium when cells are treated with trypsin (PubMed:15205117). Localized at the surface of the microvillar membrane in small intestine enterocytes, and in endosome-like structures situated beneath the microvillar membrane, and in Golgi complex (By similarity). Detected in small intestine (at protein level) (PubMed:15205117). Highly expressed in the jejunum (PubMed:15708357). N-glycosylated; required for activity and transport to the plasma membrane. Belongs to the nucleotide pyrophosphatase/phosphodiesterase family.