Dores R M, Rothenberg M E
University of Denver, Department of Biological Sciences, CO 80208.
Peptides. 1987 Nov-Dec;8(6):1119-25. doi: 10.1016/0196-9781(87)90145-8.
Acid extracts of the posterior pituitary of the amphibian, Xenopus laevis, were analyzed with two heterologous region specific beta-endorphin RIAs. Following gel filtration chromatography and cation exchange chromatography four peaks of immunoreactivity were detected. All four peaks were detected with a N-acetyl specific beta-endorphin RIA. Peak I represented 92% of the total immunoreactivity isolated following cation exchange chromatography. This peak had a net positive charge at pH 2.5 of +1 and an apparent molecular weight of 1.4 Kd. Following reverse phase HPLC, Peak I fractionated into two peaks: Peak Ia and Peak Ib. Both peaks were detected with the N-acetyl specific beta-endorphin RIA and a Met-enkephalin RIA, however, neither peak co-migrated with either Met-enkephalin or N-acetyl-beta-endorphin(1-16). At present it is not clear whether Peak I is derived from pro-opiomelanocortin or one of the other opioid polyproteins. Peaks II, III, and IV represented 8% of the total immunoreactivity recovered following cation exchange chromatography. These peaks had net positive charges of +3, +4, and +5, respectively, and apparent molecular weights of 2.8, 3.2, and 3.5 Kd, respectively. These apparently N-acetylated beta-endorphin-sized forms are minor end products of the pro-opiomelanocortin biosynthetic pathway.
用两种异源区域特异性β-内啡肽放射免疫分析法对两栖动物非洲爪蟾脑垂体后叶的酸性提取物进行了分析。经凝胶过滤色谱法和阳离子交换色谱法后，检测到四个免疫反应峰。用N-乙酰基特异性β-内啡肽放射免疫分析法检测到了所有四个峰。峰I占阳离子交换色谱法分离得到的总免疫反应性的92%。该峰在pH 2.5时的净正电荷为+1，表观分子量为1.4千道尔顿。经反相高效液相色谱法后，峰I分离为两个峰：峰Ia和峰Ib。用N-乙酰基特异性β-内啡肽放射免疫分析法和甲硫氨酸脑啡肽放射免疫分析法都检测到了这两个峰，然而，这两个峰都不与甲硫氨酸脑啡肽或N-乙酰-β-内啡肽(1-16)共迁移。目前尚不清楚峰I是源自阿黑皮素原还是其他阿片样多蛋白之一。峰II、峰III和峰IV占阳离子交换色谱法回收的总免疫反应性的8%。这些峰的净正电荷分别为+3、+4和+5，表观分子量分别为2.8、3.2和3.5千道尔顿。这些明显经N-乙酰化的β-内啡肽大小的形式是阿黑皮素原生物合成途径的次要终产物。
