Choline or its derived compounds play an essential role in many physiological processes:
- Phospholipids, especially phosphatidyl choline (PC), are found in large quantities in all biological membranes. There, they play an important role in their structure and functions, such as the transmission of signals and the transport of substances.
- Metabolism and transport of lipids and cholesterol – Fats and cholesterol from food are transported to the liver by means of chylomycrons (lipoprotein particles). From there, they are transported via the blood to extrahepatic (“outside the liver“) tissues in another type of lipoproteins (complexes of proteins (apolipoproteins), cholesterol, triglycerides, and phospholipids) called VLDLs (very low density lipoproteins). PC is necessary for the proper “manufacturing” and secretion of VLDLs.
- Choline is also of great importance in methyl group metabolism, in which homocysteine can be methylated (addition of CH 3 groups) by two different pathways. In one reaction, betaine, which is a choline derivative, serves as a methyl group donor (donor) for the methylation of homocysteine to methionine and is converted to dimethylglycine via betaine-homocysteine methyltransferase. In the second reaction, 5-methyl-tetrahydrofolate serves as a methyl donor and vitamin B12-dependent methionine synthase is the relevant enzyme.
- Choline is also a precursor of acetylcholine, a neurotransmitter (messenger substances that transmit the excitation of a nerve cell to other cells at chemical synapses). This is important for functions such as memory storage or muscle control.
