Sundler R
J Biol Chem. 1975 Nov 25;250(22):8585-90.
Ethanolaminephosphate cytidylyltransferase (EC 2.7.7.14), which catalyzes a central step in phosphatidylethanolamine synthesis, has been purified 1000-fold from a postmicrosomal supernatant from rat liver. The enzyme, which requires a reducing agent, like dithiothreitol, for activity, is stable for weeks at 0-4 degrees when stored in the presence of dithiothreitol and in the pH range 7.5 to 9.0. A molecular weight of 100 to 120 X 10(3) was estimated by gel chromatography on Sephadex G-200. Gel electrophoresis in the presence of sodium dodecyl sulfate gave only one protein band with an apparent molecular weight of 49 to 50 X 10(3). The reaction catalyzed by the enzyme is reversible with a Keq for the forward reaction of 0.46 under the assay conditions. Michaelis constants of 53 and 65 muM were determined for CTP and ethanolaminephosphate, respectively. From the product inhibition pattern an ordered sequential reaction mechanism is proposed, in which CTP is the first substrate to add to the enzyme and CDP-ethanolamine is the last product to be released. The possible role of this reaction in the regulation of phosphatidylethanolamine synthesis in liver is discussed.
乙醇胺磷酸胞苷酰转移酶（EC 2.7.7.14）催化磷脂酰乙醇胺合成中的关键步骤，已从大鼠肝脏微粒体后上清液中纯化了1000倍。该酶的活性需要还原剂，如二硫苏糖醇，当在二硫苏糖醇存在下且pH值在7.5至9.0范围内储存时，可在0-4摄氏度下稳定数周。通过Sephadex G-200凝胶色谱法估计分子量为100至120×10³。在十二烷基硫酸钠存在下进行凝胶电泳，仅出现一条表观分子量为49至50×10³的蛋白带。在测定条件下，该酶催化的反应是可逆的，正向反应的Keq为0.46。分别测定CTP和乙醇胺磷酸的米氏常数为53和65μM。根据产物抑制模式，提出了一种有序的顺序反应机制，其中CTP是第一个添加到酶上的底物，CDP-乙醇胺是最后一个释放的产物。讨论了该反应在肝脏磷脂酰乙醇胺合成调节中的可能作用。
