Watkinson A, Dockray G J, Young J, Gregory H
MRC Secretory Control Research Group, University of Liverpool, England, U.K.
J Neurochem. 1988 Oct;51(4):1252-7. doi: 10.1111/j.1471-4159.1988.tb03094.x.
Previous studies suggest the processing of proenkephalin A in the porcine upper digestive tract might differ from that in the brain. To characterise more precisely some of the products, we have used antibodies to Met-enkephalin Arg6Phe7 (MERF) in radioimmunoassay to monitor the isolation of immunoreactive peptides from extracts of porcine pyloric antral muscle, antral mucosa, and duodenum. Sephadex G50 gel filtration of each extract produced a single broad peak of high-molecular-weight MERF-immunoreactivity. On anion-exchange chromatography the antral muscle MERF-immunoreactivity fractionated into two major peaks, and that from the antral mucosa and duodenum each into four major peaks, suggesting tissue specific processing of proenkephalin A within the porcine gut. Reverse-phase HPLC and Edman degradation analysis revealed that the least acidic antral muscle peptide was a 31-residue N-terminally extended form of MERF that is equivalent to proenkephalin A 209-239. Alkaline phosphatase digestion of the N-terminally extended MERF variants indicated that some of these peptides were modified by phosphorylation. We conclude that there are complex patterns of proenkephalin A processing in the porcine gut, which in part are due to phosphorylation.
以往的研究表明，猪上消化道中脑啡肽原A的加工过程可能与大脑中的不同。为了更精确地表征其中一些产物，我们在放射免疫分析中使用了针对甲硫氨酸脑啡肽精氨酸6苯丙氨酸7（MERF）的抗体，以监测从猪幽门窦肌、窦黏膜和十二指肠提取物中分离免疫反应性肽的情况。对每种提取物进行葡聚糖凝胶G50凝胶过滤，产生了一个单一的高分子量MERF免疫反应性宽峰。在阴离子交换色谱上，窦肌MERF免疫反应性部分分离为两个主要峰，而来自窦黏膜和十二指肠的部分则各自分离为四个主要峰，这表明猪肠道内脑啡肽原A存在组织特异性加工。反相高效液相色谱和埃德曼降解分析表明，酸性最低的窦肌肽是一种31个残基的N端延伸形式的MERF，相当于脑啡肽原A 209 - 239。对N端延伸的MERF变体进行碱性磷酸酶消化表明，其中一些肽被磷酸化修饰。我们得出结论，猪肠道中存在复杂的脑啡肽原A加工模式，部分原因是磷酸化。
