The possible functional significance of phosphatidylethanolamine methylation
The possible functional significance of phosphatidylethanolamine methylation
复制标题
磷脂酰乙醇胺甲基化的可能功能意义
作者：
D. Vance;B. Kruijff
Bremer和greenberg首次报道了大鼠肝微粒体中磷脂酰乙醇胺向磷脂酰胆碱的转化。该反应需要s -腺苷-蛋氨酸连续三次甲基化乙醇胺部分。该酶在肝微粒体中活性最高，最近从大鼠肝脏中提取的酶被溶解并部分纯化。虽然活性在肝脏中最高，但它是该组织中合成磷脂酰胆碱的次要途径3。最近在牛肾上腺髓质中发现了这种酶，并且有报道称磷脂酰乙醇胺甲基转移酶在红细胞鬼影5、网织红细胞鬼影6、7和乳腺膜中具有活性8。鉴于甲基化途径在肝脏磷脂酰胆碱生物合成中的重要性相对较小，我们对磷脂甲基化引起的显著生理变化的报道很感兴趣6 - 9。本文报道的计算表明，网状红细胞、红细胞和乳腺膜中的酶活性是肝微粒体中观察到的酶活性的0.1%。此外，在观察到红细胞膜微粘度显著变化的条件下，只有极少量的磷脂酰乙醇胺被甲基化9。由于这些和其他原因，对于磷脂酰乙醇胺的甲基化能否解释归因于该活性的许多生理反应存在相当大的疑问。
The conversion of phosphatidylethanolamine to phosphatidylcholine was first reported in rat liver microsomes by Bremer and Greenberg1. The reaction requires three successive methylations of the ethanolamine moiety by S-adenosyl-methionine. The highest activity for this enzyme has been found in liver microsomes and the enzyme from rat liver was recently solubilized and partially purified2. Although the activity is highest in liver, it is the minor pathway in this tissue for the synthesis of phosphatidylcholine3. The enzyme has recently been identified in bovine adrenal medulla4 and reports exist on the activity of phosphatidylethanolamine methyltransferase in erythrocyte ghosts5, reticulocyte ghosts6,7 and mammary gland membranes8. In view of the relatively minor importance of the methylation pathway in phosphatidylcholine biosynthesis in liver, we were intrigued by the reports of significant physiological changes attributed to phospholipid methylation6–9. Calculations reported here show that this enzymatic activity in reticulocytes, erythrocytes and mammary gland membranes is 0.1% of that observed in liver microsomes. Furthermore, in conditions where marked changes in microviscosity of the erythrocyte membrane were observed, only extremely small amounts of phosphatidylethanolamine were methylated9. For these and other reasons, there is considerable doubt that methylation of phosphatidylethanolamine could account for the many physiological responses attributed to this activity.