【作者】 黄云；

【导师】 董守良；

【作者基本信息】 兰州大学 ， 生物化学与分子生物学， 2008， 硕士

【摘要】 昆虫激肽（Insect kinins）是一类以Phe-Xaa-Yaa-Trp-Gly-NH₂为C末端的多肽,其中Xaa可以是Tyr、His、Ser或Asn。Yaa可以是Ala,但通常是Ser或Pro。生物活性研究表明,它具有促进昆虫马氏管扭动及其原尿分泌、调节血淋巴量以及水盐平衡、对马氏管跨膜电位去极化、促进后肠收缩等作用。此外,还发现昆虫激肽能抑制昆虫体内蛋白水解酶、脂肪酶等消化酶的释放、抑制幼虫增长等。从结构上看,C端五肽Phe-Xaa-Yaa-Trp-Gly-NH₂是保持活性所需的最小片段,被称为核心五肽。构象研究表明,C端五肽中存在两种构象:1-4β-转角和2-5β-转角。然而,其不确切的构效关系,大大阻碍了以其结构为模板的新型害虫防治试剂的开发。本文旨在通过引入可光致异构化的硫代酰胺键ψ[CS-N],构建构象可控的昆虫激肽类似物,用以阐明C端五肽H-Phe-Xaa-Yaa-Trp-Gly-NH₂的活性构象。本文描述了昆虫激肽硫代类似物H-Phe¹-Tyr²-ψ[CS-N]-Pro³-Trp⁴-Gly⁵-NH₂（ψ[CS-N]²-kinin）的合成;并用UV-vis、CD、HPLC等方法对其光致异构化特性进行表征。结果表明:与天然肽键仅一个原子差异的硫代酰胺键有光控开关的作用:经254 nm紫外光照后,顺式ψ[CS-N]含量由15.7%增加到47.7%,通过热弛豫又下降至15.2%;热弛豫半衰期t_1/2=40 min。对其在不同构象状态下的促蟑螂后肠收缩活性研究显示:ψ[CS-N]²-kinin保留了母肽80%的最大活性,EC₅₀=（4.1±0.2）×10^-7;在254 nm紫外光照而达到光稳定状态时,ψ[CS-N]²-kinin的促后肠收缩活性比未光照状态显著增强,EC₅₀=（1.1±0.2）×10^-7;经热弛豫后,其活性又恢复到未光照水平,EC₅₀=（3.9±0.3）×10^-7。以上实验证据表明,有利于形成1-4β-转角的顺式ψ[CS-N]²-kinin是昆虫激肽类似物产生生理活性时的活性构象。更多还原

【Abstract】 The insect kinins share a highly conserved C-terminal pentapeptide sequence Phe-Xaa-Yaa-Trp-Gly-NH₂,where Xaa can be Tyr,His,Ser or Asn,and Yaa can be Ala but is generally Ser or Pro.They have been isolated from a number of insects, including species of Dictyoptera,Lepidoptera,and Orthoptera.Structurally,the insect kinins require an intact C-terminal pentapeptide sequence for full bioactivity, which was therefore designated as the active core sequence.Conformation studies indicated that there are two distinct conformation with aβ-turn over residue 1-4 and 2-5,respectively.In order to obtain a more direct evidence for the active one of these two distinct conformations,a kinin analog containing a thioxopeptide bondΨ[CS-N], a nearly isosteric modification of the native peptide bond,which can be used as a photoswitch,was synthesized.The reversible photoswitching property was characterized via spectroscopic methods and HPLC,which showed that the cis conformer increased from 15.7%to 47.7%after 254 nm UV irradiation.A slow thermal reisomerization(t_1/2=40 min) permitted us to determine the cockroach hindgut myotropic activity of the thioxopeptide in photostationary state.The results indicated that the activity increased significantly after UV irradiation and recovered to the ground level after thermal re-equilibration.In the present work,which utilizing the phototriggered isomerization in a specific position of peptide backbone,revealed that the cisΨ[CS-N]²-kinin conformer is the active conformation when interact with kinin receptor on cockroach hindgut.更多还原