Accepted name: ceramide cholinephosphotransferase
Reaction: CDP-choline + a ceramide = CMP + sphingomyelin
Glossary: a ceramide = an N-acylsphingosine
Other name(s): phosphorylcholine-ceramide transferase
Systematic name: CDP-choline:N-acylsphingosine cholinephosphotransferase
1.  Kennedy, E.P. Phosphorylcholine-glyceride transferase. Methods Enzymol. 5 (1962) 484–486.
2.  Sribney, M. and Kennedy, E.P. The enzymatic synthesis of sphingomyelin. J. Biol. Chem. 233 (1958) 1315–1322. [PMID: 13610834]
[EC created 1965]
Accepted name: sphingomyelin synthase
Reaction: a ceramide + a phosphatidylcholine = a sphingomyelin + a 1,2-diacyl-sn-glycerol
Glossary: sphingomyelin = a ceramide-1-phosphocholine
ceramide = an N-acylsphingoid. The fatty acids of naturally occurring ceramides range in chain length from about C16 to about C26 and may contain one or more double bonds and/or hydroxy substituents at C-2
sphingoid = sphinganine, i.e. D-erythro-2-aminooctadecane-1,3-diol, and its homologues and stereoisomers (see also Lip-1.4)
Other name(s): SM synthase; SMS1; SMS2
Systematic name: ceramide:phosphatidylcholine cholinephosphotransferase
Comments: The reaction can occur in both directions [3]. This enzyme occupies a central position in sphingolipid and glycerophospholipid metabolism [4]. Up- and down-regulation of its activity has been linked to mitogenic and pro-apoptotic signalling in a variety of mammalian cell types [4]. Unlike EC, ceramide cholinephosphotransferase, CDP-choline cannot replace phosphatidylcholine as the donor of the phosphocholine moiety of sphingomyelin [2].
1.  Ullman, M.D. and Radin, N.S. The enzymatic formation of sphingomyelin from ceramide and lecithin in mouse liver. J. Biol. Chem. 249 (1974) 1506–1512. [PMID: 4817756]
2.  Voelker, D.R. and Kennedy, E.P. Cellular and enzymic synthesis of sphingomyelin. Biochemistry 21 (1982) 2753–2759. [PMID: 7093220]
3.  Huitema, K., van den Dikkenberg, J., Brouwers, J.F. and Holthuis, J.C. Identification of a family of animal sphingomyelin synthases. EMBO J. 23 (2004) 33–44. [PMID: 14685263]
4.  Tafesse, F.G., Ternes, P. and Holthuis, J.C. The multigenic sphingomyelin synthase family. J. Biol. Chem. 281 (2006) 29421–29425. [PMID: 16905542]
5.  Yamaoka, S., Miyaji, M., Kitano, T., Umehara, H. and Okazaki, T. Expression cloning of a human cDNA restoring sphingomyelin synthesis and cell growth in sphingomyelin synthase-defective lymphoid cells. J. Biol. Chem. 279 (2004) 18688–18693. [PMID: 14976195]
[EC created 2006]
Accepted name: phospholipase C
Reaction: a phosphatidylcholine + H2O = 1,2-diacyl-sn-glycerol + phosphocholine
Other name(s): lipophosphodiesterase I; lecithinase C; Clostridium welchii α-toxin; Clostridium oedematiens β- and γ-toxins; lipophosphodiesterase C; phosphatidase C; heat-labile hemolysin; α-toxin
Systematic name: phosphatidylcholine cholinephosphohydrolase
Comments: The bacterial enzyme, which is a zinc protein, also acts on sphingomyelin and phosphatidylinositol; that from seminal plasma does not act on phosphatidylinositol.
1.  Druzhinina, K.V. and Kritzman, M.G. [Lecithinase from animal tissues.] Biokhimiya 17 (1952) 77–81. [PMID: 13066482] (in Russian)
2.  Little, C. and Otnass, A.-B. The metal ion dependence of phospholipase C from Bacillus cereus. Biochim. Biophys. Acta 391 (1975) 326–333. [PMID: 807246]
3.  Sheiknejad, R.G. and Srivastava, P.N. Isolation and properties of a phosphatidylcholine-specific phospholipase C from bull seminal plasma. J. Biol. Chem. 261 (1986) 7544–7549. [PMID: 3086312]
4.  Takahashi, T., Sugahara, T. and Ohsaka, A. Purification of Clostridium perfringens phospholipase C (α-toxin) by affinity chromatography on agarose-linked egg-yolk lipoprotein. Biochim. Biophys. Acta 351 (1974) 155–171. [PMID: 4365891]
[EC created 1961]
Accepted name: sphingomyelin phosphodiesterase
Reaction: a sphingomyelin + H2O = a ceramide + phosphocholine
Glossary: a ceramide = an N-acylsphingosine
Other name(s): neutral sphingomyelinase
Systematic name: sphingomyelin cholinephosphohydrolase
Comments: Has very little activity on phosphatidylcholine.
1.  Barnholz, Y., Roitman, A. and Gatt, S. Enzymatic hydrolysis of sphingolipids. II. Hydrolysis of sphingomyelin by an enzyme from rat brain. J. Biol. Chem. 241 (1966) 3731–3737. [PMID: 5916388]
2.  Chatterjee, S. and Ghosh, N. Neutral sphingomyelinase from human urine. Purification and preparation of monospecific antibodies. J. Biol. Chem. 264 (1989) 12554–12561. [PMID: 2545711]
3.  Heller, M. and Shapiro, B. Enzymic hydrolysis of sphingomyelin by rat liver. Biochem. J. 98 (1966) 763–769. [PMID: 5911524]
4.  Kanfer, J.N., Young, O.M., Shapiro, D. and Brady, R.O. The metabolism of sphingomyelin. I. Purification and properties of a sphingomyelin-cleaving enzyme from rat liver tissue. J. Biol. Chem. 241 (1966) 1081–1084. [PMID: 5933867]
[EC created 1972]
Accepted name: sphingomyelin phosphodiesterase D
Reaction: sphingomyelin + H2O = ceramide phosphate + choline
Other name(s): sphingomyelinase D
Systematic name: sphingomyelin ceramide-phosphohydrolase
Comments: Does not act on phosphatidylcholine, but hydrolyses 2-lysophosphatidylcholine to choline and 2-lysophosphatidate.
1.  Carne, H.R. and Onon, E. Action of Corynebacterium ovis exotoxin on endothelial cells of blood vessels. Nature 271 (1978) 246–248. [PMID: 622164]
2.  Soucek, A., Michalec, C. and Souckov, A. Identification and characterization of a new enzyme of the group phospholipase D isolated from Corynebacterium ovis. Biochim. Biophys. Acta 227 (1971) 116–128. [PMID: 5543581]
[EC created 1978]
Accepted name: sphingomyelin deacylase
Reaction: (1) an N-acyl-sphingosylphosphorylcholine + H2O = a fatty acid + sphingosylphosphorylcholine
(2) a D-glucosyl-N-acylsphingosine + H2O = a fatty acid + D-glucosyl-sphingosine
Glossary: sphingomyelin = N-acyl-sphingosylphosphorylcholine
D-glucosyl-N-acylsphingosine = glucosylceramide
Other name(s): SM deacylase; GcSM deacylase; glucosylceramide sphingomyelin deacylase; sphingomyelin glucosylceramide deacylase; SM glucosylceramide GCer deacylase; SM-GCer deacylase; SMGCer deacylase
Systematic name: N-acyl-sphingosylphosphorylcholine amidohydrolase
Comments: The enzyme is involved in the sphingolipid metabolism in the epidermis.
1.  Hara, J., Higuchi, K., Okamoto, R., Kawashima, M. and Imokawa, G. High-expression of sphingomyelin deacylase is an important determinant of ceramide deficiency leading to barrier disruption in atopic dermatitis. J. Invest. Dermatol. 115 (2000) 406–413. [PMID: 10951276]
2.  Higuchi, K., Hara, J., Okamoto, R., Kawashima, M. and Imokawa, G. The skin of atopic dermatitis patients contains a novel enzyme, glucosylceramide sphingomyelin deacylase, which cleaves the N-acyl linkage of sphingomyelin and glucosylceramide. Biochem. J. 350 (2000) 747–756. [PMID: 10970788]
3.  Ishibashi, M., Arikawa, J., Okamoto, R., Kawashima, M., Takagi, Y., Ohguchi, K. and Imokawa, G. Abnormal expression of the novel epidermal enzyme, glucosylceramide deacylase, and the accumulation of its enzymatic reaction product, glucosylsphingosine, in the skin of patients with atopic dermatitis. Lab. Invest. 83 (2003) 397–408. [PMID: 12649340]
[EC created 2011]
Accepted name: P-type phospholipid transporter
Reaction: ATP + H2O + phospholipid[side 1] = ADP + phosphate + phospholipid[side 2]
Other name(s): Mg2+-ATPase (ambiguous); flippase (ambiguous); aminophospholipid-transporting ATPase (ambiguous); phospholipid-translocating ATPase (ambiguous); phospholipid-transporting ATPase (ambiguous)
Systematic name: ATP phosphohydrolase (P-type, phospholipid-flipping)
Comments: A P-type ATPase that undergoes covalent phosphorylation during the transport cycle. Different forms of the enzyme move phospholipids such as phosphatidylcholine, lyso-phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidyglycerol, sphingomyelin and glucosylceramide from one membrane face to the other (‘flippase’).
1.  Morris, M.B., Auland, M.E., Xu, Y.H. and Roufogalis, B.D. Characterization of the Mg2+-ATPase activity of the human erythrocyte membrane. Biochem. Mol. Biol. Int. 31 (1993) 823–832. [PMID: 8136700]
2.  Vermeulen, W.P., Briede, J.J. and Rolofsen, B. Manipulation of the phosphatidylethanolamine pool in the human red cell membrane affects its Mg2+-ATPase activity. Mol. Membr. Biol. 13 (1996) 95–102. [PMID: 8839453]
3.  Suzuki, H., Kamakura, M., Morii, M. and Takeguchi, N. The phospholipid flippase activity of gastric vesicles. J. Biol. Chem. 272 (1997) 10429–10434. [PMID: 9099684]
4.  Auland, M.E., Roufogalis, B.D., Devaux, P.F. and Zachowski, A. Reconstitution of ATP-dependent aminophospholipid translocation in proteoliposomes. Proc. Natl. Acad. Sci. USA 91 (1994) 10938–10942. [PMID: 7971987]
5.  Alder-Baerens, N., Lisman, Q., Luong, L., Pomorski, T. and Holthuis, J.C. Loss of P4 ATPases Drs2p and Dnf3p disrupts aminophospholipid transport and asymmetry in yeast post-Golgi secretory vesicles. Mol. Biol. Cell 17 (2006) 1632–1642. [PMID: 16452632]
6.  Lopez-Marques, R.L., Poulsen, L.R., Hanisch, S., Meffert, K., Buch-Pedersen, M.J., Jakobsen, M.K., Pomorski, T.G. and Palmgren, M.G. Intracellular targeting signals and lipid specificity determinants of the ALA/ALIS P4-ATPase complex reside in the catalytic ALA α-subunit. Mol. Biol. Cell 21 (2010) 791–801. [PMID: 20053675]
7.  Jensen, M.S., Costa, S.R., Duelli, A.S., Andersen, P.A., Poulsen, L.R., Stanchev, L.D., Gourdon, P., Palmgren, M., Günther Pomorski, T. and Lopez-Marques, R.L. Phospholipid flipping involves a central cavity in P4 ATPases. Sci. Rep. 7:17621 (2017). [PMID: 29247234]
[EC created 2000 as EC (EC created 2000, incorporated 2001), transferred 2018 to EC]