Kinetic and topographical studies of the phosphatidylcholine: ceramide choline phosphotransferase in plasma membrane particles from mouse ascites cells.

The content of endogenous phospholipids in plasma membrane preparations from Ehrlich ascites cells was depleted by exposure to phospholipase C. The enzyme catalyzing the phosphatidylcholine: ceramide choline phosphotransferase reaction was inactivated by this treatment. However, the activity could be restored with exogenous phosphatidylcholines, demonstrating the dependence of the reaction upon the presence of this substrate.

The phosphorylcholine acceptor in the phosphatidylcholine:ceramide cholinephosphotransferase reaction. Is the enzyme a transferase or a hydrolase?

The cholinephosphotransferase reaction is shown to be catalyzed by an enzyme which has no hydrolytic activity and which is different from a phospholipase C type activity also present in these plasma membrane preparations. Diacylglycerols and sphingosine, at a concentration above 0.4 mM, are effective inhibitors of sphingomyelin formation in the presence of 0.

[Surgical interventions on the gallbladder and the biliary tract in the aged].

The surgery of the gall bladder by gallstones, bile duct and alterations of the duodenal papilla are conducted with an increase of lethality. This increased lethality is caused by accompanying ill effects, especially chronical pancreatitis, cholangitis, disturbances of the liver. The indications to operate old patients are occlusions of duodenal papilla relapsing colics with or less occlusing icterus, emphysema of gall bladder or perforation.

The role of endogenous phosphatidylcholine and ceramide in the biosynthesis of sphingomyelin in mouse fibroblasts.

The intracellular location of sphingomyelin formation via the cholinephosphotransferase reaction from both endogenous an exogenous phosphatidylcholine and ceramide substrates has been studied in the subcellular membrane fractions prepared from mouse fibroblasts. The enzyme was found to be located in both the plasma membrane and the Golgi fractions. Activity in the Golgi fraction was stimulated to a greater extent by the addition of exogenous ceramide than was the activity in the plasma membrane fraction.

The formation of sphingomyelin from phosphatidylcholine in plasma membrane preparations from mouse fibroblasts.

The enzymatic formation of radioactive sphingomyelin from [14C]choline-labeled phosphatidylcholine was demonstrated to reside exclusively in the plasma membrane fraction of mouse fibroblasts. This activity has several properties in common with the phosphatidylcholine ceramide phosphocholine transferase of mouse liver microsomes. The enzyme has little if any phospholipase C activity and isotope dilution experiments suggest that phosphatidylcholine is the substrate rather than it is converted to CDP choline, phosphocholine, free choline or glycerophosphocholine prior to the transfer reaction.