Sohal P S, Cornell R B
Institute of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
J Biol Chem. 1990 Jul 15;265(20):11746-50.
We report CTP:phosphocholine cytidylyltransferase (CT) as another target enzyme of sphingosine actions in addition to the well-characterized protein kinase C. Effects of sphingosine and lysophingolipids were studied on the activity of purified cytidylyltransferase prepared by the method of Weinhold et al. (Weinhold, P. A., Rounsifer, M.E., and Feldman, D.A. (1986) J. Biol. Chem. 261, 5104-5110). The sphingolipids were tested as components of egg phosphatidylcholine (PC) vesicles, 25 mol% sphingosine inhibited the CT activity by about 50%. The inhibition of CT by sphingosine and lysosphingolipids was reversible. Sphingosine was found to be a reversible inhibitor of CT with respect to the activating lipids such as phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, and fatty acid:phosphatidylcholine vesicles. Egg PC vesicles containing sphingosine, psychosine (galactosylsphingosine), glucopsychosine (glucosylsphingosine), and lysosphingomyelin (sphingosylphosphorylcholine) suppressed the activation by PC/oleic acid vesicles, whereas the parent sphingolipids did not. Egg PC vesicles containing oleylamine and hexadecyltrimethylamine inhibited CT activity, whereas egg PC-octylamine vesicles did not alter the enzyme activity. This indicates the importance of an amino group and long alkyl chain. LysoPC, a known detergent, did not inhibit the enzyme activity under the same assay conditions in which sphingosine inhibited. These results are the first report of a lipid inhibitor of purified CT.
我们报道了CTP：磷酸胆碱胞苷转移酶（CT）是鞘氨醇作用的另一个靶酶，除了已被充分研究的蛋白激酶C。采用Weinhold等人（Weinhold, P. A., Rounsifer, M.E., and Feldman, D.A. (1986) J. Biol. Chem. 261, 5104 - 5110）的方法制备纯化的胞苷转移酶，研究了鞘氨醇和溶血鞘脂对其活性的影响。鞘脂作为卵磷脂酰胆碱（PC）囊泡的成分进行测试，25摩尔%的鞘氨醇抑制CT活性约50%。鞘氨醇和溶血鞘脂对CT的抑制是可逆的。相对于磷脂酰丝氨酸、磷脂酰肌醇、磷脂酰甘油和脂肪酸：磷脂酰胆碱囊泡等激活脂质，鞘氨醇是CT的可逆抑制剂。含有鞘氨醇、鞘氨醇半乳糖苷（半乳糖基鞘氨醇）、鞘氨醇葡萄糖苷（葡萄糖基鞘氨醇）和溶血鞘磷脂（鞘氨醇磷酸胆碱）的卵PC囊泡抑制了PC/油酸囊泡的激活作用，而相应的亲本鞘脂则没有。含有油胺和十六烷基三甲基胺的卵PC囊泡抑制CT活性，而卵PC - 辛胺囊泡则不改变酶活性。这表明氨基和长烷基链的重要性。溶血PC是一种已知的去污剂，在鞘氨醇抑制的相同测定条件下不抑制酶活性。这些结果是关于纯化CT的脂质抑制剂的首次报道。
