[29] Choline-phosphate cytidylyltransferase

Publisher Summary Choline-phosphate cytidylyltransferase (CTP:cholinephosphate cytidylyltransferase) catalyzes a major rate-determining step in the biosynthesis of phosphatidylcholine in mammalian cells. Both cytosolic and membrane fractions contain choline-phosphate cytidylyltransferase activity. Enzyme activity is determined by measuring the formation of radioactive CDPcholine from phospho[methyl- 14 C]choline. Two methods have been used to separate CDPcholine from phosphocholine: adsorption of CDPcholine by charcoal or separation of CDPcholine from phosphocholine by thin-layer chromatography. The charcoal adsorption method is rapid, sensitive, and reproducible. The ability to perform many assays (50–100) per day is an additional advantage. A variety of lipids have been used by investigators for the assay of cytidylyltransferase. It has been a common practice to include lipid in assays involving soluble forms of cytidylyltransferase. The molecular and kinetic properties of cytidylyltransferase are discussed this chapter.