phosphatidylcholine 2mM: sphingomyelin ~0.5mM mM
||Human Homo sapiens
||Wargo MJ. Homeostasis and catabolism of choline and glycine betaine: lessons from Pseudomonas aeruginosa. Appl Environ Microbiol. 2013 Apr79(7):2112-20. doi: 10.1128/AEM.03565-12. p.2113 left column 2nd paragraphPubMed ID23354714
|| Hidaka H et al., 2008. Specific, rapid, and sensitive enzymatic measurement of sphingomyelin, phosphatidylcholine and lysophosphatidylcholine in serum and lipid extracts. Clin. Biochem. 41: 1211–1217. doi: 10.1016/j.clinbiochem.2008.06.010.PubMed ID18619432
||Primary source abstract: "Design and methods: The total choline-containing phospholipids (total PL), SM (sphingomyelin) and PC (phosphatidylcholine) were measured using a two-reagent system involving specific enzymes for choline-based phospholipids. The procedure was performed using either microplate or automatic analyzer technology. The concentration of lyso-PC was calculated by subtracting the concentration of SM plus PC from the total PL concentration."
||P.2113 left column 2nd paragraph: "Soluble choline is measurable in some environments (∼8 μM in serum, 0 to 45 nM in seawater [BNID 112935]), but the most abundant source is thought to be the choline headgroup moiety on the eukaryotic phospholipids phosphatidylcholine and sphingomyelin, which together typically comprise 50 to 90% of the outer leaflet of eukaryotic plasma membranes (BNID 112936). Phosphatidylcholine and sphingomyelin are also abundant in human serum, at 2 mM and ∼0.5 mM, respectively (primary source)."