Albi E, Viola Magni M
Facoltà di Medicina e Chirurgia, Università degli Studi di Perugia, Policlinico Monteluce, Perugia, 06100, Italy.
Biochem Biophys Res Commun. 1999 Nov 30;265(3):640-3. doi: 10.1006/bbrc.1999.1710.
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 investigated if phosphatidylcholine-dependent phospholipase C could be present in the nuclei. The results obtained have shown the presence of this enzyme 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 regeneration. In the chromatin an increase of activity has been shown 12 h and 30 h after hepatectomy, i.e. at the beginning of hepatocyte S-phase. No similar behaviour has been observed in the nuclear membrane. It has been suggested that diacylglicerol, produced by the hydrolysis of chromatin phosphatidylcholine, may have a role in initiating DNA synthesis through the prolonged activation of the nuclear form of protein kinase C.
磷脂酰胆碱依赖性磷脂酶C是一种能水解磷脂酰胆碱生成二酰甘油和磷酸胆碱的酶。二酰甘油具有多种作用，还能激活蛋白激酶C。由于已证实在肝细胞核中存在蛋白激酶C，且在染色质中存在磷脂部分，我们研究了磷脂酰胆碱依赖性磷脂酶C是否存在于细胞核中。所得结果表明，在染色质部分存在这种酶，其在pH值和Km方面与核膜的不同。还在肝再生过程中评估了该活性。在染色质中，肝切除术后12小时和30小时，即肝细胞S期开始时，活性增加。在核膜中未观察到类似行为。有人提出，染色质磷脂酰胆碱水解产生的二酰甘油可能通过长期激活核形式的蛋白激酶C在启动DNA合成中起作用。
