Kadowaki H, Grant M A
Department of Medicine, Boston University School of Medicine, MA 02118, USA.
J Lipid Res. 1995 Jun;36(6):1274-82.
The ceramide molecular species specificity of rat brain neuron CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase (LacCer alpha 2,3-ST) was determined using 19 molecular species of lactosylceramide incorporated into liposomes prepared with purified rat brain phospholipids. The neuron enzyme displayed a distinct molecular species specificity (which was different than the specificity of liver LacCer alpha 2,3-ST) based on both the long-chain base and the fatty acid composition of the lactosylceramide. Specifically, compared to the liver enzyme, relatively high activities were obtained with d18:1-16:0, d18:1-22:1, and d18:0-18:0 lactosylceramide molecular species. When the lipid composition of the neuron microsomal membranes was altered to resemble that of rat liver Golgi membrane lipids, the activities towards d18:1-16:0, d18:1-22:1, and d18:0-18:0 lactosylceramide molecular species were significantly (P < 0.01) reduced and the molecular species specificity of the neuron enzyme resembled that of liver LacCer alpha 2,3-ST. In the reciprocal experiment in which the lipid composition of the rat liver Golgi membranes was altered to resemble neuron microsomal membrane lipids, the molecular species specificity of liver LacCer alpha 2,3-ST was virtually identical to the specificity obtained with the native neuron enzyme. Analysis of the molecular species composition of lactosylceramide and GM3 in rat liver Golgi membranes revealed that the molecular species composition of rat liver Golgi membrane GM3 was precisely what would be expected based on the molecular species specificity of LacCer alpha 2,3-ST and the molecular species composition of lactosylceramide in the Golgi membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
利用19种乳糖基神经酰胺分子种类，测定大鼠脑神经元CMP-N-乙酰神经氨酸：乳糖基神经酰胺α2,3-唾液酸转移酶（LacCer α2,3-ST）的神经酰胺分子种类特异性，这些乳糖基神经酰胺被掺入用纯化的大鼠脑磷脂制备的脂质体中。基于乳糖基神经酰胺的长链碱基和脂肪酸组成，神经元酶表现出独特的分子种类特异性（不同于肝脏LacCer α2,3-ST的特异性）。具体而言，与肝脏酶相比，d18:1-16:0、d18:1-22:1和d18:0-18:0乳糖基神经酰胺分子种类具有相对较高的活性。当神经元微粒体膜的脂质组成改变为类似于大鼠肝脏高尔基体膜脂质时，对d18:1-16:0、d18:1-22:1和d18:0-18:0乳糖基神经酰胺分子种类的活性显著（P<0.01）降低，且神经元酶的分子种类特异性类似于肝脏LacCer α2,3-ST。在反向实验中，大鼠肝脏高尔基体膜的脂质组成改变为类似于神经元微粒体膜脂质，肝脏LacCer α2,3-ST的分子种类特异性与天然神经元酶获得的特异性几乎相同。对大鼠肝脏高尔基体膜中乳糖基神经酰胺和GM3的分子种类组成分析表明，大鼠肝脏高尔基体膜GM3的分子种类组成正是基于LacCer α2,3-ST的分子种类特异性和高尔基体膜中乳糖基神经酰胺的分子种类组成所预期的。（摘要截断于250字）
