DeVries G H, Zetusky W J, Zmachinski C, Calabrese V P
J Lipid Res. 1981 Feb;22(2):208-16.
The lipid composition was determined for axolemma-enriched fractions and myelin which were isolated via a preparation of purified myelinated axons. The myelin had a lipid composition which was compatible with that previously reported for myelin isolated by alternative procedures. The most dense axolemma-enriched fraction contained 25.3% cholesterol, 25.8% galactolipid (21.3% cerebrosides and 4.8% sulfatides), and 48.9% phospholipid. The major phospholipids were the ethanolamine phospholipid (19.8% of total lipid weight; 49.0% in the plasmalogen form) and choline phospholipids (18.7% of total lipid weight; 16.0% in the plasmalogen form) with lesser amounts of sphingomyelin, phosphatidylserine, and phosphatidylinositol also present; the ganglioside content was 13.9 micrograms of acetylneuraminic acid per mg protein. The less dense axolemma-enriched fraction had a lipid composition which was intermediate between that of myelin and the more dense axolemma-enriched fraction. On the average, less than 2.3% of the total protein in the axolemma-enriched fraction was myelin basic protein. Both axolemma-enriched fractions stained uniformly with Luxol fast blue and demonstrated specific saxitoxin-binding which was enriched 2- to 7-fold over that of the whole white matter homogenate from which the fractions were isolated. The choline and ethanolamine phospholipids in that most dense axolemma-enriched fractions contained a greater percentage of unsaturated fatty acids compared with the comparable phospholipids in myelin. The content of unsaturated fatty acids in these phospholipids of the axolemma-enriched fraction was not as great as that of human CNS synaptic plasma membranes. However, the chain length distribution of these phospholipid fatty acids was similar in myelin, synaptic plasma membrane, and the axolemma-enriched fraction. The distribution of aldehydes derived from the ethanolamine phospholipids of the more dense axolemma-enriched fraction closely resemble the distribution of the comparable aldehydes in the myelin fraction. The possible origin and function of the lipids in the axolemma-enriched fractions are discussed.
通过纯化有髓轴突的制备方法，对富含轴膜的组分和髓磷脂的脂质组成进行了测定。该髓磷脂的脂质组成与先前通过其他方法分离得到的髓磷脂的脂质组成相符。密度最大的富含轴膜的组分含有25.3%的胆固醇、25.8%的半乳糖脂（21.3%的脑苷脂和4.8%的硫脂）以及48.9%的磷脂。主要的磷脂是乙醇胺磷脂（占总脂质重量的19.8%；49.0%为缩醛磷脂形式）和胆碱磷脂（占总脂质重量的18.7%；16.0%为缩醛磷脂形式），同时还存在少量的鞘磷脂、磷脂酰丝氨酸和磷脂酰肌醇；神经节苷脂含量为每毫克蛋白质13.9微克的N - 乙酰神经氨酸。密度较小的富含轴膜的组分的脂质组成介于髓磷脂和密度较大的富含轴膜的组分之间。平均而言，富含轴膜的组分中总蛋白的不到2.3%是髓磷脂碱性蛋白。两个富含轴膜的组分用卢氏固蓝均匀染色，并显示出特异性的石房蛤毒素结合，其比分离出这些组分的整个白质匀浆中的结合量富集了2至7倍。与髓磷脂中相应的磷脂相比，密度最大的富含轴膜的组分中的胆碱和乙醇胺磷脂含有更高百分比的不饱和脂肪酸。富含轴膜的组分中这些磷脂的不饱和脂肪酸含量不如人中枢神经系统突触质膜中的高。然而，这些磷脂脂肪酸的链长分布在髓磷脂膜、突触质膜和富含轴膜的组分中是相似的。密度较大的富含轴膜的组分中乙醇胺磷脂衍生的醛的分布与髓磷脂组分中相应醛的分布非常相似。文中讨论了富含轴膜的组分中脂质的可能来源和功能。
