Nakajima M, Taguchi R, Ikezawa H
Toxicon. 1987;25(5):555-64. doi: 10.1016/0041-0101(87)90291-1.
The effects of phospholipases C on the equilibrium constants and maximal binding capacities of tritiated [D-Ala2,-D-Leu5] enkephalin to rat brain membranes were investigated using phosphatidylcholine-hydrolyzing phospholipase C and sphingomyelinase C of Bacillus cereus and, phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis. When 72% of the phosphatidylinositol in the rat brain membranes was hydrolyzed by phosphatidylinositol-specific phospholipase C, the affinity of opiate receptor for [D-Ala2,-D-Leu5] enkephalin was almost doubled and maximal binding of [D-Ala2,-D-Leu5] enkephalin was decreased to 87% of control. Although specific [D-Ala2,-D-Leu5] enkephalin binding was decreased with phosphatidylinositol hydrolysis when measured at higher concentration (30 nM) of [D-Ala2,-D-Leu5] enkephalin, the specific binding was increased with the hydrolysis of phosphatidylinositol when measured at lower concentration (6 nM) of the ligand. On treatment of membranes with phosphatidylcholine-hydrolyzing phospholipase C, specific [D-Ala2,-D-Leu5] enkephalin binding was drastically decreased with the progressive hydrolysis of phosphatidylcholine in the rat brain membranes, and specific binding was completely lost after 81% hydrolysis of phosphatidylcholine. However, the affinity of opiate receptor for [D-Ala2,-D-Leu5] enkephalin was not influenced, and maximal binding was decreased to 32% of the control when 61% of phosphatidylcholine was hydrolyzed. Treatment with sphingomyelinase C did not cause any appreciable reduction of specific [D-Ala2,-D-Leu5] enkephalin binding. From these results, it is concluded that the binding of [D-Ala2,-D-Leu5] enkephalin to opiate receptor is influenced by changes in the phospholipid environment of the rat brain membranes, and that phosphatidylinositol may be a modulator for the function of the receptor.
利用蜡状芽孢杆菌的磷脂酰胆碱水解磷脂酶C和鞘磷脂酶C以及苏云金芽孢杆菌的磷脂酰肌醇特异性磷脂酶C，研究了磷脂酶C对氚标记的[D-丙氨酸2，-D-亮氨酸5]脑啡肽与大鼠脑膜的平衡常数和最大结合容量的影响。当大鼠脑膜中72%的磷脂酰肌醇被磷脂酰肌醇特异性磷脂酶C水解时，阿片受体对[D-丙氨酸2，-D-亮氨酸5]脑啡肽的亲和力几乎增加了一倍，而[D-丙氨酸2，-D-亮氨酸5]脑啡肽的最大结合量降至对照的87%。尽管在较高浓度（30 nM）的[D-丙氨酸2，-D-亮氨酸5]脑啡肽下测量时，特异性[D-丙氨酸2，-D-亮氨酸5]脑啡肽结合随磷脂酰肌醇水解而降低，但在较低浓度（6 nM）的配体下测量时，特异性结合随磷脂酰肌醇水解而增加。用磷脂酰胆碱水解磷脂酶C处理脑膜时，随着大鼠脑膜中磷脂酰胆碱的逐步水解，特异性[D-丙氨酸2，-D-亮氨酸5]脑啡肽结合急剧下降，在磷脂酰胆碱水解81%后特异性结合完全丧失。然而，阿片受体对[D-丙氨酸2，-D-亮氨酸5]脑啡肽的亲和力未受影响，当61%的磷脂酰胆碱被水解时，最大结合量降至对照的32%。用鞘磷脂酶C处理未导致特异性[D-丙氨酸2，-D-亮氨酸5]脑啡肽结合有任何明显降低。从这些结果可以得出结论，[D-丙氨酸2，-D-亮氨酸5]脑啡肽与阿片受体的结合受大鼠脑膜磷脂环境变化的影响，并且磷脂酰肌醇可能是该受体功能的调节剂。
