phosphocholine

Phosphocholine, also known as phosphorylcholine, is a zwitterionic molecule that serves as a key intermediate in cellular phospholipid metabolism. It is the phosphomonoester of choline and acts as a precursor in the biosynthesis of phosphatidylcholine, a major component of cell membranes.

Chemically, phosphocholine consists of a quaternary ammonium group from choline linked through a phosphate monoester. At physiological pH it behaves as a zwitterion, with a permanently positive charge on the choline nitrogen and a negative charge on the phosphate group, contributing to its hydrophilic character.

Biosynthesis and metabolism are centered in the Kennedy pathway. Choline is first phosphorylated by choline kinase to form phosphocholine, which is then converted to CDP-choline by CTP:phosphocholine cytidylyltransferase. CDP-choline can subsequently transfer the phosphocholine moiety to diacylglycerol to yield phosphatidylcholine. Phosphocholine can also arise transiently during phospholipid turnover and phospholipase–mediated hydrolysis, producing glycerophosphocholine and choline as downstream products.

Biological roles and relevance include its function as a building block for membrane phospholipids and as a metabolite measured in cellular lipid metabolism. In clinical and research settings, phosphocholine is sometimes detected as part of the total choline-containing compounds in magnetic resonance spectroscopy, a marker of membrane turnover and cellular proliferation in some cancers. It is commonly discussed alongside related molecules such as glycerophosphocholine and phosphatidylcholine.

See also: phosphatidylcholine, glycerophosphocholine, choline, Kennedy pathway.