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 cgd3_2030
Choline-phosphate cytidylyltransferase 2.7.7.15 cgd8_1150
Diacylglycerol choline phosphotransferase 2.7.8.2 cgd4_2790
Diacylglycerol choline phosphotransferase 2.7.8.2 cgd4_390
Phospholipase A2 3.1.1.4 cgd2_4050
Phospholipase A2 3.1.1.4 cgd7_2630
Lysophospholipase 3.1.1.5 cgd6_4080
Phospholipase C 3.1.4.3 cgd4_2560
Glycerophosphodiester phosphodiesterase 3.1.4.46 cgd5_490
SEC14 none cgd1_1240
SEC14 none cgd3_1550
SEC14 none cgd8_3790

 

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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