Lindberg I, White L
Arch Biochem Biophys. 1986 Feb 15;245(1):1-7. doi: 10.1016/0003-9861(86)90183-9.
To shed light on the evolution of the opioid peptide precursor proenkephalin, we have investigated the profile of immunoreactive enkephalins in reptilian brain using six antisera directed toward different portions of the proenkephalin molecule. Three different orders of reptiles--turtles, alligators, and lizards--were studied; these orders represent lineages diverging more than 250 million years ago. Reptilian brain was found to contain large quantities of Met5-enkephalin (Met5-enk), Leu5-enkephalin (Leu5-enk), and Met5-enk-Arg6-Phe7 (MERF); gel filtration and reverse-phase chromatography of acid extracts prepared from turtle brain indicated that nearly all of the immunoreactivity corresponding to these peptides could be ascribed to the authentic penta- to heptapeptides. Immunoreactive metorphamide, but not amidorphin, was present in all three species. Unlike mammalian brain, reptilian brain does not contain immunoreactive Met5-enk-Arg6-Gly7-Leu8 (MERGL). These results indicate that reptilian proenkephalin, while similar to mammalian enkephalin in containing Met5-enk, Leu5-enk, MERF, and metorphamide, nevertheless differs from mammalian proenkephalin. Reptilian proenkephalin either may contain the MERGL sequence in a form not recognized by the MERGL antibody, or may lack the MERGL sequence entirely.
为了阐明阿片肽前体脑啡肽原的进化过程，我们使用了六种针对脑啡肽原分子不同部分的抗血清，研究了爬行动物大脑中免疫反应性脑啡肽的分布情况。我们研究了三种不同目级别的爬行动物——龟、短吻鳄和蜥蜴；这三个目代表了在超过2.5亿年前就已分化的谱系。结果发现，爬行动物大脑中含有大量的甲硫氨酸脑啡肽（Met5-enk）、亮氨酸脑啡肽（Leu5-enk）和甲硫氨酸脑啡肽-精氨酸-苯丙氨酸（MERF）；对龟脑制备的酸提取物进行凝胶过滤和反相色谱分析表明，几乎所有与这些肽对应的免疫反应性都可归因于真正的五肽至七肽。在所有这三个物种中都存在免疫反应性的甲硫氨酸酰胺化脑啡肽，但不存在酰胺化脑啡肽。与哺乳动物大脑不同，爬行动物大脑中不含有免疫反应性的甲硫氨酸脑啡肽-精氨酸-甘氨酸-亮氨酸（MERGL）。这些结果表明，爬行动物的脑啡肽原虽然在含有甲硫氨酸脑啡肽、亮氨酸脑啡肽、MERF和甲硫氨酸酰胺化脑啡肽方面与哺乳动物的脑啡肽相似，但仍与哺乳动物的脑啡肽原有所不同。爬行动物的脑啡肽原要么可能以一种不被MERGL抗体识别的形式包含MERGL序列，要么可能完全缺乏MERGL序列。
