Biosyntesis and Physiological action of vasoactive peptides

为了了解垂体腺苷酸环化酶激活多肽（垂体腺苷酸环化酶激活多肽，垂体腺苷酸环化酶激活多肽，PACAP）是一种类似神经肽的新型血管活性肠多肽，其受体及其在心血管控制中的可能生理功能，本文对其结构和活性关系进行了研究。采用固相多肽合成器，采用Fmoc策略合成PACAP及其相关肽。采用圆二色光谱、2D ^1H核磁共振光谱、距离几何、精细分子动力学和能量最小化计算相结合的方法，研究了PACAP38和PACAP27在含不同量三氟乙醇水溶液中的溶液结构。PACAP38的初始无序n端结构域为8个氨基酸，第9 ~ 20、21 ~ 26位为α -螺旋结构域，第28 ~ 34位为短α -螺旋结构域。PACAP27的结构与PACAP38非常相似，但c端螺旋没有磨损。PACAP38和PACAP27在犬股血流和离体豚鼠血管中具有与VIP相似的强效血管扩张作用。PAVAP38的作用持续时间是其他药物的3-4倍。在狗和猪的消化系统中，PACAP38和PACAP27收缩胆囊，刺激胰液、碳酸氢盐和蛋白质的分泌。另一方面，VIP放松了孤立的胆囊条。在犬体内，PACAP通过胆碱能神经间接作用于胰腺和胆囊，而在体外则是直接作用于胰腺和胆囊。这些结果表明，PACAP的血管扩张作用位于n端，与VIP序列同源性高。PACAP38的c端结构对作用持续时间有重要影响。不同于VIP的n端PACAP序列负责刺激胆碱能神经和胆囊平滑肌。

In order to understand the molecular recognition of pituitary adenylate cyclase activating polypeptide (PACAP), a new vasoactive intestinal polypeptide (VIP) like neuropeptide, by its receptors and possible physiological function in cardiovascular control, the structure and activity relationship was investigated. PACAP and their related peptides were synthesized by the Fmoc strategy using a solid phase peptide synthesizer. Solution structures of PACAP38 and PACAP27 were studied in aqueous solution containing varying amounts of trifluoroethanol by circular dichroism spectroscopy and a combination of 2D ^1H nuclear magnetic resonance spectroscopy, distance geometry, and refined molecular dynamics and energy minimization calculations. PACAP38 had an initial disordered N-terminal domain of 8 amino acids, followed by an alpha-helical structure from 9th to 20th, 21st to 26th, and a short alpha-helix between 28th and 34th. The structure of PACAP27 was closely similar to that of PACAP38 but showed no fraying of the C-terminal helix. PACAP38 and PACAP27 had a potent vasodilator action similar to that of VIP in femoral blood flow in dogs and in the isolated quinea pig blood vessels. The effect of PAVAP38 lasted 3-4 times longer that the others. In the digestive system of dogs and quinea pigs, PACAP38 and PACAP27 contracted the gallbladder and stimulated pancreatic fluid, bicarbonate and protein secretion. VIP, on the other hand, relaxed the isolated gall-bladder strips. PACAP acts on the pancreas and gallbladder indirectly via cholinergic nerves in dogs, but its effect in vitro was a direct one These results suggests that vasodilator action of PACAP resides in N-terminal region, where it has high sequence homology with VIP. The C-terminal structure of PACAP38 is important for the duration of effect. The N-terminal PACAP sequence distinct from VIP is responsible for stimulation of cholinergic nerves and gallbladder smooth muscle.