TABLE 1.

Characteristics and details of pulmonary surfactant proteins and surfactant lipids.

Name	Size	Chemistry	Major functions	Ref
SP-A	28–36 kDa	Hydrophilic	Involved in facilitating phagocytosis, inhibition of phospholipase A2 activity and maintaining surfactant integrity during lung injury	[1]
		Octadecameric glycoprotein, acidic
SP-B	8 kDa	Hydrophobic.	Involved in decreasing the surface tension and enhancing adsorption of PL at air-water interface. Deficiency results in severe respiratory failure	[2]
		Disulfide linked homodimer with 79 amino acids (AA)
SP-C	4.2 kDa	Hydrophobic.	Involved in stabilizing phospholipids, increasing the viscosity of air-water interfacial film	[2]
		α-helical protein with 35 AA	Deficiency results in minimal effect on respiratory function
SP-D	43 kDa	Hydrophilic. Dodecameric glycoprotein with 4 trimmers	Involved in regulating surfactant metabolism and promotes phagocytosis by alveolar cells	[3]
1,2-Dipalmitoyl-sn-glycero-3-phosphatidylcholine	734.05 gmol-1	PC16:0/16:0, C40H80NO8P	Involved in the generation of near-zero surface tension	[3]
1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)	760.09 gmol-1	PC 16:0/18:1	Involved in making the membrane fluid at body temperature	[3,4]
		C42H82NO8P
1-Palmitoyl-2-palmitoleoyl-sn-glycero-3-phosphocholine (PPPC)	732.04 gmol-1	PC 16:0/16:1, C40H78NO8P	Involved in regulating respiratory rate and surface dynamics of surfactant	[3,4]
1-Palmitoyl-2-myristoyl-sn-glycero-3-phosphocholine	706 gmol-1	PC16:0/14:0, C38H76NO8P	Involved in regulating respiratory rate and alveolar macrophages function to improve protection	[4,5]
1,2-Dipalmitoyl- sn-glycero-3-phosphoglycerol (DPPG)	722.98 gmol-1	C38H75O10P	Involved in reducing permeability of benzo [a]pyrene	[4,5]
1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG)	749.02 gmol-1	C40H77O10P	The most abundant PG in human pS. Enhances fluidization of film, inhibits macrophage proinflammatory responses and antiviral	[4,5]
Phosphatidylserine	792.09 gmol-1	C42H82NO10P	Involved in determining the cellular and subcellular distribution of quinidine	[2,4]
PE	299.22 gmol-1	C9H18NO8P	Involved in stabilizing membrane protein by initiation of lateral pressure and curvature stress	[2,4]
Phosphatidylinositol	334.21 gmol-1	C9H19O11P	Involved in increasing the rate of alveolar fluid clearance and stabilization of surfactant mono layer	[4,6]
Cholesterol	386.66 gmol-1	C17H46O	Involved in increasing the surfactant fluidity	[4,7]

Note: AA, amino acid; DPPC, dipalmityl phophotidylcholine; PE, phosphatidylethanolamine; PS, Pulmonary surfactant; SP, surfactant protein; C, Carbon; H, Hydrogen: O, Oxygen; p, Phosphorus; N, Nitrogen.

References.

[1] J.A. Whitsett, The molecular era of surfactant biology, Neonatology. 105 (2014) 337–343. doi:10.1159/000360649.

[2] F.P.S. Yu, D. Islam, J. Sikora, S. Dworski, J. Gurka, L. López-Vásquez, M. Liu, W.M. Kuebler, T. Levade, H. Zhang, J.A. Medin, Chronic lung injury and impaired pulmonary function in a mouse model of acid ceramidase deficiency., Am. J. Physiol. Lung Cell. Mol. Physiol. 314 (2018) L406–L420. doi:10.1152/ajplung.00223.2017.

[3] F. Wang, J. Liu, H. Zeng, Interactions of particulate matter and pulmonary surfactant: Implications for human health., Adv. Colloid Interface Sci. 284 (2020) 102,244. doi:10.1016/j.cis. 2020.102,244.

[4] S.E. Wert, J.A. Whitsett, L.M. Nogee, Genetic disorders of surfactant dysfunction, Pediatr. Dev. Pathol. 12 (2009) 253–274. doi:10.2350/09–01-0,586.1.

[5] U. Klenz, M. Saleem, M.C. Meyer, H.J. Galla, Influence of lipid saturation grade and headgroup charge: A refined lung surfactant adsorption model, Biophys. J. 95 (2008) 699–709. doi:10.1529/biophysj.108.131,102.

[6] D.R. Voelker, M. Numata, Phospholipid regulation of innate immunity and respiratory viral infection., J. Biol. Chem. 294 (2019) 4,282–4,289. doi:10.1074/jbc.AW118.003229.

[7] A. Kelly, C. McCarthy, Pulmonary Alveolar Proteinosis Syndrome., Semin. Respir. Crit. Care Med. 41 (2020) 288–298. doi:10.1055/s-0039–3402,727.