This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Fatty Acids and Lipids Biosynthesis → Phospholipid Biosynthesis → Phosphatidylcholine Biosynthesis|
Expected Taxonomic Range: Viridiplantae
Phosphatidylcholine is one of the major constituents of membrane phospholipids (see phospholipid biosynthesis II). The phosphatidylcholine biosynthetic pathways vary among different organisms.
There are at least four alternative routes have been reported in plants. Two additional routes were reported in animals [Schneider79] and bacteria [Sohlenkamp00] (see pathways phosphatidylcholine biosynthesis V and phosphatidylcholine biosynthesis VI).
1) The Kennedy pathway (phosphatidylcholine biosynthesis I) depends on choline kinase and on the availability of choline.
2) The second pathway (depicted here) depends on three consecutive N-methylation steps that are carried out on phospho-bases, phosphoethanolamine, phospho-N-methylethanolamine, and phospho-N-dimethylethanolamine.
3) The third pathway (phosphatidylcholine biosynthesis III) depends on an initial N-methylation with phospho-base phosphoethanolamine, and followed by two downstream N-methylations on phosphatidyl-bases, phosphatidyl-N-methylethanolamine and phosphatidyl-N-dimethylethanolamine. In plants, phosphatidyl-N-methylethanolamine is believed to be derived from CDP-methylethanolamine, whereas in animals, it is a direct methylation product from phosphatidylethanolamine [Schneider79].
4) The fourth pathway (phosphatidylcholine biosynthesis IV) depends on two N-methylations with phospho-base phosphoethanolamine and phospho-N-methylethanolamine, followed by a downstream N-methylation on phosphatidyl-base phosphatidyl-N-dimethylethanolamine.
Radio tracer experiments with crude cell extracts suggested such a pathway in Lemna and carrot [Datko88a], but not in soybean. An Arabidopsis gene (AtNMT1) was isolated through functional complementation of a yeast mutant deficient in phosphatidylcholine. Assay of the AtNMT1 recombinant enzyme indicated that it catalyzes three sequential methylations of phosphoethanolamine to form phosphocholine [Bolognese00].
Variants: phosphatidylcholine biosynthesis I , phosphatidylcholine biosynthesis III , phosphatidylcholine biosynthesis IV , phosphatidylcholine biosynthesis V , phosphatidylcholine biosynthesis VI , phosphatidylcholine biosynthesis VII , phospholipid remodeling (phosphatidylcholine, yeast)
Bolognese00: Bolognese CP, McGraw P (2000). "The isolation and characterization in yeast of a gene for Arabidopsis S-adenosylmethionine:phospho-ethanolamine N-methyltransferase." Plant Physiol 124(4);1800-13. PMID: 11115895
Schneider79: Schneider WJ, Vance DE (1979). "Conversion of phosphatidylethanolamine to phosphatidylcholine in rat liver. Partial purification and characterization of the enzymatic activities." J Biol Chem 254(10);3886-91. PMID: 438165
Sohlenkamp00: Sohlenkamp C, de Rudder KE, Rohrs V, Lopez-Lara IM, Geiger O (2000). "Cloning and characterization of the gene for phosphatidylcholine synthase." J Biol Chem 275(25);18919-25. PMID: 10858449
Friesen01: Friesen JA, Park YS, Kent C (2001). "Purification and kinetic characterization of CTP:phosphocholine cytidylyltransferase from Saccharomyces cerevisiae." Protein Expr Purif 21(1);141-8. PMID: 11162399
Hjelmstad91: Hjelmstad RH, Bell RM (1991). "sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases in Saccharomyces cerevisiae. Mixed micellar analysis of the CPT1 and EPT1 gene products." J Biol Chem 266(7);4357-65. PMID: 1847919
Jones98b: Jones PL, Willey DL, Gacesa P, Harwood JL (1998). "Isolation, characterisation and expression of a cDNA for pea cholinephosphate cytidylyltransferase." Plant Mol Biol 37(1);179-85. PMID: 9620275
Nishida96: Nishida I, Swinhoe R, Slabas AR, Murata N (1996). "Cloning of Brassica napus CTP: phosphocholine cytidylyltransferase cDNAs by complementation in a yeast cct mutant." Plant Mol Biol 31(2);205-11. PMID: 8756587
Nuccio00: Nuccio ML, Ziemak MJ, Henry SA, Weretilnyk EA, Hanson AD (2000). "cDNA cloning of phosphoethanolamine N-methyltransferase from spinach by complementation in Schizosaccharomyces pombe and characterization of the recombinant enzyme." J Biol Chem 275(19);14095-101. PMID: 10799484
Wang90a: Wang X, Moore TS Jr (1990). "Phosphatidylcholine biosynthesis in castor bean endosperm. Purification and properties of cytidine 5'-triphosphate:choline-phosphate cytidylyltransferase." Plant Physiol. 93; 250-255.
©2014 SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493