Wednesday 4 January 2012
Definition: Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup. They are a major component of biological membranes.
The phospholipid is composed of a choline head group and glycerophosphoric acid with a variety of fatty acids, one being a saturated fatty acid (in the example, here palmitic or hexadecanoic acid, H3C-(CH2)14-COOH; margaric acid identified by Gobley in egg yolk, or heptadecanoic acid H3C-(CH2)15-COOH, also belong to that class); and one being an unsaturated fatty acid (here oleic acid, or 9Z-octadecenoic acid, as in Gobley’s original egg yolk lecithin).
Phospholipase D catalyzes the hydrolysis of phosphatidylcholine to form phosphatidic acid (PA), releasing the soluble choline headgroup into the cytosol.
Phosphatidylcholine (lecithin) is a major constituent of cell membranes.
Phosphatidylcholine is more commonly found in the exoplasmic or outer leaflet of a cell membrane. It is thought to be transported between membranes within the cell by phosphatidylcholine transfer protein (PCTP).
Phosphatidylcholine also plays a role in membrane-mediated cell signalling and PCTP activation of other enzymes.