Activation of CTP:phosphocholine cytidylyltransferase by hypochlorite-oxidized phosphatidylcholines

Adrienne E. Drobnies, Eduard A. Venczel, Rosemary B. Cornell
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引用次数: 8

Abstract

CTP:phosphocholine cytidylyltransferase (CT) catalyzes a rate-limiting, regulatory step in mammalian biosynthesis of phosphocholine (PC). Anionic phospholipids, fatty acids and diacylglycerol activate CT and promote its intercalation into the lipid bilayer, whereas zwitterionic phospholipids such as phosphatidylcholines do not. We investigated the effectiveness of polyunsaturated phosphatidylcholines as CT activators after hypochlorite oxidation. Detection and quantitation of oxidized PCs were evaluated by thin layer chromatography, high performance liquid chromatography, and conjugated dienes. Purified CT was assayed in the presence of multilamellar vesicles, containing variable concentrations of oxidized and parent PCs. The results demonstrate that particular species of oxidized PCs activate CT as potently as anionic lipids. The greater the number of double bonds available for oxidation in the fatty acid at the sn-2 position of the PC, the more effective was the oxidized PC as an activator of CT. Oxidized phospholipids at 1:1 bleach/lipid activated CT in the following order: PAPC>PL3PC>PL2PC compared to unoxidized controls. Since oxidized phospholipids decrease bilayer order (M.L. Wratten et al., Biochemistry 31 (1992) 10901–10907) these results are consistent with the activation of CT by perturbations of lipid bilayer packing.

次氯酸氧化磷脂酰胆碱活化CTP:磷脂酰转移酶
CTP:磷脂酰转移酶(CT)催化了哺乳动物合成磷脂(PC)的一个限速、调节步骤。阴离子磷脂、脂肪酸和二酰基甘油激活CT并促进其嵌入脂质双分子层,而两性离子磷脂如磷脂酰胆碱则不会。我们研究了多不饱和磷脂酰胆碱在次氯酸氧化后作为CT活化剂的有效性。采用薄层色谱法、高效液相色谱法和共轭二烯法对氧化pc的检测和定量进行了评价。纯化的CT在含有不同浓度的氧化和母体pc的多层囊泡的情况下进行检测。结果表明,特定种类的氧化pc能像阴离子脂质一样有效地激活CT。PC sn-2位脂肪酸中可供氧化的双键数越多,氧化后的PC作为CT活化剂的效果越好。氧化磷脂在1:1漂白剂/脂质活化CT的顺序如下:与未氧化对照相比,PAPC>PL3PC>PL2PC。由于氧化磷脂降低了双分子层秩序(M.L. Wratten et al., Biochemistry 31(1992) 10901-10907),这些结果与脂质双分子层堆积的扰动激活CT一致。
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