Roy J, Johnson M, Dubin S, Gazis D C, Schwartz I L
Int J Pept Protein Res. 1980 Mar;15(3):279-84. doi: 10.1111/j.1399-3011.1980.tb02578.x.
[1-Alpha-Mercaptoacetic acid, 5-isoasparagine] oxytocin was synthesized to study the effects of moving the side chain carboxamide group of the amino acid residue in position 5 of oxytocin from the beta to the alpha position. The analog has an isoasparagine residue in position 5 and the 20-membered ring size of oxytocin is maintained by substituting cysteine in position 1 of oxytocin by alpha-mercaptoacetic acid. The analog was found to possess 0.098 +/- 0.002 U/mg of uterotonic activity but no milk-ejecting, antidiuretic or rat pressor activity could be detected. The substance did not inhibit the uterotonic or milk-ejecting activity induced by oxytocin nor the antidiuretic or rat pressor responses to the USP posterior pituitary standard. These results, together with the data available in the literature, indicate that an analog of oxytocin lacking the asparagine residue in position 5 is neither an agonist nor an antagonist. The observations may mean that the asparagine residue is critically important for the interaction of oxytocin with its receptor.
[1-α-巯基乙酸，5-异天冬酰胺]催产素被合成出来，以研究将催产素第5位氨基酸残基的侧链羧酰胺基团从β位移至α位的效果。该类似物在第5位有一个异天冬酰胺残基，并且通过用α-巯基乙酸取代催产素第1位的半胱氨酸来维持催产素的20元环大小。发现该类似物具有0.098±0.002 U/mg的子宫收缩活性，但未检测到排乳、抗利尿或大鼠升压活性。该物质既不抑制催产素诱导的子宫收缩或排乳活性，也不抑制对USP垂体后叶标准品的抗利尿或大鼠升压反应。这些结果，连同文献中的现有数据，表明在第5位缺乏天冬酰胺残基的催产素类似物既不是激动剂也不是拮抗剂。这些观察结果可能意味着天冬酰胺残基对催产素与其受体的相互作用至关重要。
