Diacylglycerol choline phosphotransferase

These studies demonstrate that choline ingested in the form of lecithin or lecithin precursors [diacylglycerol choline phosphotransferase (CDP)-choline] can improve mild memory loss associated with the aging process. Choline chloride, however, appears to be less effective than lecithin for improving memory, likely because of its lower bioavailability (300). 

McMaster, CR Bell, RM. CDP-choline 1,2-diacylglycerol choline phosphotransferase. 

PC is synthesized in plant cells via the CDP-choline pathway, which includes three enzymatic steps catalyzed by choline kinase (EC 2.7.1.32 CKI), CTPiphosphocholine cytidylyltransferase (EC 2.7.7.15 CCT) and CDP-choline diacylglycerol choline-phosphotransferase (EC 2.7.8.2 CPT). Among them, CCT has been reported to be a rate-limiting enzyme [3]. 

Some preparations of choline kinase have activity towards ethanplamine and the activities co-purify and cannot be separated. However, in most tissues separate choline and ethanolamine kinases have been found and purified. As with typical kinases. Mg-ATP is the cosubstrate. The other two enzymes involved in the sequence to phosphatidylcholine (Figure 7.1) are a cytidylyltransferase and 1,2-diacylglycerol choline phosphotransferase. Whereas choline kinase is a soluble enzyme, the cytidylyltransferase is found both in the cytosol and bound to the endoplasmic reticulum. Since the cytidylyltransferase appears to be the rate-limiting enzyme for phosphatidylcholine synthesis in both plants and animals, its regulation is particularly important. There is good evidence that in animal tissues this is... 

The type II pneumocytes synthesize phosphatidylcholine in a fashion quite different from that in other cells. Most other cells synthesize phosphatidylserine from cytidine diphosphate diacylglycerol and serine. The phosphatidylserine is then decarboxylated to yield phosphatidyl ethanoiamine. The final step is the successive donation of three methyl groups via S-adenosylmethionine to form phosphatidylcholine. The pulmonary biosynthetic pathway is shown in Figure 54-2. The enzyme choline phosphotransferase forms PC directly from cytidine diphosphocholine and diacylglycerol. Phosphatidylinositol formation peaks at about 35 weeks. As PI decreases in concentration, PG begins to increase. 

If these drugs reach the endoplasmic reticulum an altered formation of the diacylglycerol pool specific for the choline-phosphotransferase may explain the inhibition observed. The shift in the biosynthetic flow towards IPG may be due to a rapid inhibition of phos-phatidate phosphatase as a result of this CPG and EPG as well as... 

DISCRIMINATION BY MICROSOMAL CHOLINE-PHOSPHOTRANSFERASE BETWEEN MOLECULAR SPECIES OF ENDOGENOUS DIACYLGLYCEROLS... 

---