Phosphatidylcholine-dependent phospholipase C in rat liver chromatin

Phosphatidylcholine-dependent phospholipase C is an enzyme which hydrolyses phosphatidylcholine giving origin to diacylglicerol and phosphorylcholine. Diacylglicerol has many effect and activates also protein kinase C. Since the presence of protein kinase C in the hepatocyte nuclei and the existence of a phospholipidic fraction in the chromatin have been demonstrated, we i nvestigated if phosphatidylcholine-dependent phospholipase C could be prese nt in the nuclei. The results obtained have shown the presence of this enzy me in the chromatin fraction which differs with respect to that of nuclear membrane in pH and Km, The activity has been also evaluated during liver re generation. In the chromatin an increase of activity has been shown 12 h an d 30 h after hepatectomy, i.e. at the beginning of hepatocyte S-phase, No s imilar behaviour has been observed in the nuclear membrane. It has been sug gested that diacylglicerol, produced by the hydrolysis of chromatin phospha tidylcholine, may have a role in initiating DNA synthesis through the prolo nged activation of the nuclear form of protein kinase C. (C) 1999 Academic Press.