Phosphocholin

Phosphocholine, also known as phosphorylcholine, is a zwitterionic molecule consisting of a phosphate group linked to choline. It serves as the phosphocholine headgroup of phosphatidylcholine, one of the most abundant phospholipids in cellular membranes, and can also exist as a free metabolite in smaller amounts.

In biochemistry, phosphocholine is an intermediate in the CDP-choline (Kennedy) pathway for phosphatidylcholine biosynthesis. Choline is first phosphorylated by choline kinase to form phosphocholine, which is then converted to CDP-choline and subsequently transferred to diacylglycerol to generate phosphatidylcholine. Phosphocholine can also be generated when phosphatidylcholine is degraded by phospholipases.

Biological and clinical relevance: Phosphocholine is a recognizable epitope on the surfaces of certain bacteria, including Streptococcus species, where it participates in interactions with host immune components. It is known to bind C-reactive protein and certain natural antibodies, contributing to innate immune recognition and inflammation. Because of its role as a membrane headgroup and its immunological associations, phosphocholine-containing molecules are of interest in vaccines, immunology research, and lipidomics studies. In biomedical imaging and metabolomics, phosphocholine-containing lipids and their derivatives are examined to assess membrane turnover and cellular health.