:Phosphatidylglycerol
{{Short description|Lipid}}
Image:Phosphatidylglycerol.png
Phosphatidylglycerol is a glycerophospholipid found in pulmonary surfactant{{cite journal|author=Richard J. King |author2=Mary Catherine MacBeth |date=6 October 1981 |title=Interaction of the lipid and protein components of pulmonarysurfactant Role of phosphatidylglycerol and calcium |journal=Biochimica et Biophysica Acta (BBA) - Biomembranes |volume=647 |issue=2 |pages=159–168 |doi=10.1016/0005-2736(81)90242-X|pmid=6895322 }} and in the plasma membrane where it directly activates lipid-gated ion channels.
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
image:Biosynthesis of phosphatidylglycerol, phosphatidylserine, and phosphatidylethanolamine.svg
Phosphatidylglycerol (PG) is formed via a complex sequential pathway whereby phosphatidic acid (PA) is first converted to CDP-diacylglyceride by the enzyme CDP-diacylglyceride synthase.{{Cite journal |last=Dowhan |first=W. |date=1997-09-04 |title=CDP-diacylglycerol synthase of microorganisms |url=https://pubmed.ncbi.nlm.nih.gov/9370328/ |journal=Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism |volume=1348 |issue=1–2 |pages=157–165 |doi=10.1016/s0005-2760(97)00111-2 |issn=0006-3002 |pmid=9370328}} Then a PGP synthase enzyme exchanges glycerol-3-phosphate (G3P) for cytidine monophosphase (CMP), forming the temporary intermediate phosphatidylglycerolphosphate (PGP).{{Cite journal |last1=Pluschke |first1=G. |last2=Hirota |first2=Y. |last3=Overath |first3=P. |date=1978-07-25 |title=Function of phospholipids in Escherichia coli. Characterization of a mutant deficient in cardiolipin synthesis. |journal=Journal of Biological Chemistry |volume=253 |issue=14 |pages=5048–5055 |doi=10.1016/S0021-9258(17)34655-0 |doi-access=free |issn=0021-9258}} PG is finally synthesized when a PGP phosphatase enzyme catalyzes the immediate dephosphorylation of the PGP intermediate to form PG.{{Cite journal |last1=Dillon |first1=Deirdre A. |last2=Wu |first2=Wen-I |last3=Riedel |first3=Bettina |last4=Wissing |first4=Josef B. |last5=Dowhan |first5=William |last6=Carman |first6=George M. |date=November 1996 |title=The Escherichia coli pgpB Gene Encodes for a Diacylglycerol Pyrophosphate Phosphatase Activity |journal=Journal of Biological Chemistry |language=en |volume=271 |issue=48 |pages=30548–30553 |doi=10.1074/jbc.271.48.30548|doi-access=free |pmid=8940025 }} In bacteria, another membrane phospholipid known as cardiolipin can be synthesized by condensing two molecules of phosphatidylglycerol; a reaction catalyzed by the enzyme cardiolipin-synthase.{{Cite journal |last1=Nishijima |first1=S |last2=Asami |first2=Y |last3=Uetake |first3=N |last4=Yamagoe |first4=S |last5=Ohta |first5=A |last6=Shibuya |first6=I |date=February 1988 |title=Disruption of the Escherichia coli cls gene responsible for cardiolipin synthesis. |journal=Journal of Bacteriology |volume=170 |issue=2 |pages=775–780 |doi=10.1128/jb.170.2.775-780.1988 |issn=0021-9193 |pmid=2828323|pmc=210721 }} In eukaryotic mitochondria phosphatidylglycerol is converted to cardiolipin by reacting with a molecule of cytidine diphosphate diglyceride in a reaction catalyzed by cardiolipin synthase.{{cite journal |vauthors=Hostetler KY, van den Bosch H, van Deenen LL |title=The mechanism of cardiolipin biosynthesis in liver mitochondria |journal=Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism |volume=260 |issue=3 |pages=507–13 |date=March 1972 |pmid=4556770 |doi=10.1016/0005-2760(72)90065-3 |hdl=1874/17621 |s2cid=46101728 |url=|hdl-access=free }}
See also
References
{{reflist}}
- Hostetler KY, van den Bosch H, van Deenen LL. The mechanism of cardiolipin biosynthesis in liver mitochondria. Biochim Biophys Acta. 1972 Mar 23;260(3):507-13. {{doi|10.1016/0005-2760(72)90065-3}}. PMID 4556770.
External links
- {{MeshName|Phosphatidylglycerols}}
{{Phospholipids}}