Phosphatidylglycerol

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General chemical structure of a phosphatidyl glycerol where R¹ and R² are fatty acid side chains

Phosphatidylglycerol is a glycerophospholipid found in pulmonary surfactant.

The general structure of phosphatidylglycerol consists of a L-glycerol 3-phosphate backbone ester-bonded to either saturated or unsaturated fatty acids on carbons 1 and 2. The head group substituent glycerol is bonded through a phosphomonoester. It is the precursor of surfactant and its presence (>0.3) in the amniotic fluid of the newborn indicates fetal lung maturity.

Approximately 98% of alveolar wall surface area is due to the presence of type I cells, with type II cells producing pulmonary surfactant covering around 2% of the alveolar walls. Once surfactant is secreted by the type II cells, it must be spread over the remaining type I cellular surface area. Phosphatidylglycerol is thought to be important in spreading of surfactant over the Type I cellular surface area. The major surfactant deficiency in premature infants relates to the lack of phosphatidylglycerol, even though it comprises less than 5% of pulmonary surfactant phospholipids. It is synthesized by head group exchange of a phosphatidylcholine enriched phospholipid using the enzyme phospholipase D.

Biosynthesis

Biosynthesis of Phosphatidylglycerol

Phosphatidic acid reacts with CTP, producing CDP-diacylglycerol, with loss of pyrophosphate. Glycerol-3-phosphate reacts with CDP-diacylglycerol to form phosphatidylglycerol phosphate, while CMP is released. The phosphate group is hydrolysed forming phosphatidylglycerol.

Two phosphatidylglycerols form cardiolipin, the constituent molecule of the mitochondrial inner membrane.

See also

• glycerol
• cardiolipin

External links

• Phosphatidylglycerols at the US National Library of Medicine Medical Subject Headings (MeSH)