Phosphatidylcholine metabolism

Phospholipids are crucial components of the cell membrane bilayers. Most of these phospholipids are composed of a diglyceride (diacylglycerol) moiety, a phosphate group and a simple organic molecule such as choline, serine or ethanolamine. The anionic phosphate groups and polar groups such as choline form the hydrophilic heads and the fatty acid chains in diacylglycerol form the hydrophobic tails in the membrane bilayer. A phospholipid with choline as simple organic molecule is phosphatidylcholine and it is also known as lecithin.

 

The apicomplexan parasites, Plasmodium falciparum and Toxoplasma gondii can de novo synthesise phospholipids such as phosphatidylcholine and phosphatidylethanolamine from choline and ethanolamine respectively [1, 2]. The analysis of the Cryptosporidium genomes showed that they can also de novo synthesise phosphatidylcholine from choline. They also possess the enzymes which catalyse the metabolism of the phospholipids. In contrast to T. gondii phosphatidylcholine metabolism pathway, Cryptosporidium species do not possess the abilities to synthesise choline phosphate from O-phosphoethanolamine and betaine from choline.

 

Enzyme EC Number Gene id
Choline kinase 2.7.1.32 Chro.30240
Choline-phosphate cytidylyltransferase 2.7.7.15 Chro.80135
Diacylglycerol choline phosphotransferase 2.7.8.2 Chro.40053
Diacylglycerol choline phosphotransferase 2.7.8.2 Chro.40314
Phospholipase A2 3.1.1.4 Chro.20432
Phospholipase A2 3.1.1.4 Chro.70299
Lysophospholipase 3.1.1.5 Chro.60469
Phospholipase C 3.1.4.3 Chro.40288
Glycerophosphodiester phosphodiesterase 3.1.4.46 Chro.50344
SEC14 none Chro.10145
SEC14 none Chro.30187
SEC14 none Chro.80436

 

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Sources and fates of metabolites

 

Substrate Source pathways Product Fate pathways
Choline Host Phosphatidylcholine Phosphatidylethanolamine and phosphatidylserine metabolism
S-adenosylmethionine Methionine metabolism S-adenosylhomocysteine Methionine metabolism
1,2-Diacylglycerol Phosphatidylethanolamine and phosphatidylserine metabolism, Inositol phosphate metabolism sn-glycerol-3P Phosphatidylethanolamine and phosphatidylserine metabolism