Amiche M, Sagan S, Mor A, Delfour A, Nicolas P
Laboratory of Peptide Bioactivation, Jacques Monod Institute, University of Paris, France.
Int J Pept Protein Res. 1988 Dec;32(6):506-11. doi: 10.1111/j.1399-3011.1988.tb01381.x.
Amphibian skin synthesizes a variety of biologically active peptides. Of these, dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2) is an extraordinarily potent opioid peptide up to 1000 times more active than morphine in inducing analgesia after intracerebroventricular administration. Dermorphin has little in common with the sequence of all hitherto known mammalian opioid peptides and is unique in having a D-amino acid residue in position 2. Specific binding properties of tritium labeled dermorphin were characterized in the rat brain. Scatchard or Hill analysis of equilibrium measurements performed over a large range of concentrations revealed a single population of dermorphin binding sites with a Kd value of 0.46 nM. Dermorphin and the selective mu-receptor ligand (D-Ala2, MePhe4, Gly5-ol)-enkephalin (DAGO) had similar high potencies in competing with (3H)-dermorphin binding, whereas the inverse holds for the prototypical delta receptor ligand (D-Pen2, D-Pen5)-enkephalin (DPDPE), which exhibited a potency three orders of magnitude lower. Dermorphin was tested for its relative affinity to mu and delta binding sites by determining its potency in displacing (3H)-DAGO and (3H)-DPDPE from rat brain membrane preparations. Based on these comparisons, dermorphin exhibited a selectivity ratio Ki(DPDPE)/Ki(DAGO) = 100, a value almost identical to that of DAGO, this ligand being considered as the protypical mu-receptor probe. The high affinity and selectivity of (3H)-dermorphin together with its very low nonspecific binding make this peptide a useful tool for dissecting the role(s) of the mu-receptor(s).
两栖动物的皮肤能合成多种生物活性肽。其中，皮啡肽（Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2）是一种极其强效的阿片样肽，脑室内给药后诱导镇痛的活性比吗啡高1000倍。皮啡肽与所有迄今已知的哺乳动物阿片样肽序列几乎没有共同之处，其独特之处在于第2位有一个D-氨基酸残基。用氚标记的皮啡肽在大鼠脑中的特异性结合特性进行了表征。对在大范围浓度下进行的平衡测量进行Scatchard或Hill分析，发现单一的皮啡肽结合位点群体，其解离常数（Kd）值为0.46 nM。皮啡肽和选择性μ受体配体（D-Ala2，MePhe4，Gly5-ol）-脑啡肽（DAGO）在与（3H）-皮啡肽结合的竞争中具有相似的高效能，而典型的δ受体配体（D-Pen2，D-Pen5）-脑啡肽（DPDPE）则相反，其效能低三个数量级。通过测定皮啡肽从大鼠脑膜制剂中置换（3H）-DAGO和（3H）-DPDPE的效能，测试了其对μ和δ结合位点的相对亲和力。基于这些比较，皮啡肽的选择性比率Ki（DPDPE）/Ki（DAGO）=100，该值几乎与DAGO相同，DAGO被认为是典型的μ受体探针。（3H）-皮啡肽的高亲和力和选择性以及其极低的非特异性结合，使其成为剖析μ受体作用的有用工具。
