Arias H R, Barrantes F J
Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur and Consejo de Investigaciones Científicas y Técnicas, 8000 Bahía Blanca, Argentina.
Neurochem Int. 1987;11(1):101-6. doi: 10.1016/0197-0186(87)90155-0.
Phospholipid phosphate group metabolism has been studied in the electrocyte of Discopyge tschudii (Torpedinidae), following for several hours the incorporation and distribution of [(32)P] in living electrocyte stacks and acetylcholine receptor membranes prepared therefrom. Conditions are reported for the incubation of electrocyte columns in vitro with [(32)P]O(4)Na(2)H resulting in active and sustained incorporation of the precursor in minority phospholipids. Phosphatidic acid, phosphatidylinositol, phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate, representing 2.3, 2.1, 0.3 and 0.2% respectively of the total phospholipids were almost exclusively labelled. Relative specific activities of 13, 7, 56 and 140 respectively were attained. These values were much higher than those of major phospholipids like phosphatidylcholine (0.03) or phosphatidylethanolamine (0.01). Subcellular fractionation of the metabolically active electrocyte stacks yielded various membrane fractions differing in their degree of [(32)P]-labelling, specially in phosphatidic acid and polyphosphoinositides. The fraction richest in nicotinic acetylcholine receptor protein showed the highest levels of [(32)P] incorporation. The results indicate that phosphorylation reactions are actively operative in certain phospholipid classes of the electrocyte and in membranes obtained from these cells after in vitro labelling with [(32)P]. In particular, phosphomonoester groups in polyphosphoinositides and the phosphate group in phosphatidic acid display a high metabolic activity.
在电鳐（电鳐科）的电细胞中研究了磷脂磷酸基团代谢，在数小时内追踪了[(32)P]在活电细胞堆叠体及其制备的乙酰胆碱受体膜中的掺入和分布情况。报告了用电细胞柱在体外与[(32)P]O(4)Na(2)H孵育的条件，结果导致前体在少数磷脂中活性且持续地掺入。磷脂酸、磷脂酰肌醇、磷脂酰肌醇 - 4 - 磷酸和磷脂酰肌醇 - 4,5 - 二磷酸分别占总磷脂的2.3%、2.1%、0.3%和0.2%，几乎被专一性标记。分别获得了13、7、56和140的相对比活性。这些值远高于主要磷脂如磷脂酰胆碱（0.03）或磷脂酰乙醇胺（0.01）的值。对代谢活跃的电细胞堆叠体进行亚细胞分级分离，得到了不同[(32)P]标记程度的各种膜分级分离物，特别是在磷脂酸和多磷酸肌醇方面。富含烟碱型乙酰胆碱受体蛋白的分级分离物显示出最高水平的[(32)P]掺入。结果表明，磷酸化反应在电细胞的某些磷脂类别以及这些细胞经[(32)P]体外标记后获得的膜中活跃地起作用。特别是，多磷酸肌醇中的磷酸单酯基团和磷脂酸中的磷酸基团显示出高代谢活性。
