The effect of beta-turn structure on the passive diffusion of peptides across Caco-2 cell monolayers
The effect of beta-turn structure on the passive diffusion of peptides across Caco-2 cell monolayers
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DOI：
10.1023/a:1012152117703
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发表时间：
1997-10-01
影响因子：
3.7
通讯作者：
Borchardt, RT
中科院分区：
文献类型：
--
作者：
Knipp, GT;Velde, DGV;Borchardt, RT
目的。研究肽的 β 转角结构与其在 Caco-2 细胞单层（肠粘膜体外模型）中被动扩散之间的关系。方法。合成了线性亲水肽（Ac-TyrProXaaZaaVal-NH2；Xaa = Gly，lie和Zaa = Asp，Asn）和疏水肽（Ac-Yaa-ProXaaIleVal-NH2；Yaa = Tyr，Phe和Xaa = Gly，lie：和Ac-PheProXaane-NH2；Xaa = Gly，lie）肽及其有效渗透系数(P-eff) 是在 Caco-2 单层细胞上测定的。通过测量1-辛醇和HBSS之间的分配系数（P-o/w）来估计肽的亲脂性。使用二维核磁共振（2D-NMR）光谱和圆二色性（CD）光谱来确定这些模型肽的溶液结构。结果。使用2D-NMR光谱和CD光谱，亲水性含Gly肽（Ac-TyrProGlyZaaVal-NH2; Zaa = Asp、Asn）在溶液中表现出比含 Ile 的肽（Ac-TyrProIleZaaVal-NH2；Zaa = Asp、Asn）更高程度的 β 转角结构；CD 光谱用于显示含 Gly 的疏水性肽（Ac-YaaProGlyIleVal-NH2；Yaa = Tyr；Phe：和 Ac-PheProGlyIle-NH2）表现出更高程度的 β 转角结构。与含 Lie 的疏水性肽相比，在未受干扰的 Caco-2 细胞单层中，所有四种亲水性肽的 P-eff 值都非常低，并且在 Asp 或 Asn 系列中，含 Gly 和含 Lie 的五肽之间没有观察到统计学上的显着差异。 Phe 系列中的四肽表现出高渗透性，代谢不稳定。相比之下，Tyr 系列中含甘氨酸和 Lie 的五肽以及 Phe 系列中含 Lie 的五肽和四肽表现出低渗透性，代谢稳定。结论：通过 log P-o/w 测量，在溶液中表现出显着 β 转角结构的疏水性肽更具亲脂性，并且更容易。与缺乏这种类型溶液结构的疏水性肽相比，这些肽通过跨细胞途径渗透 Caco-2 细胞单层的能力也使它们暴露于代谢，可能是通过胞质内肽酶进行的。单层。
Purpose. To investigate the relationships between the beta-turn structure of a peptide and its passive diffusion across Caco-2 cell monolayers, an in vitro model of the intestinal mucosa.Methods. Linear hydrophilic peptides (Ac-TyrProXaaZaaVal-NH2; Xaa = Gly, lie and Zaa = Asp, Asn) and hydrophobic (Ac-Yaa-ProXaaIleVal-NH2; Yaa = Tyr, Phe and Xaa = Gly, lie: and Ac-PheProXaane-NH2; Xaa = Gly, lie) peptides were synthesized and their effective permeability coefficients (P-eff) were determined across Caco-2 cell monolayers. The lipophilicities of the peptides were estimated by measuring their partition coefficients (P-o/w between 1-octanol and HBSS. Two-dimensional NMR (2D-NMR) spectroscopy and circular dichroism (CD) spectroscopy was used to determine the solution structures of these model peptides.Results. Using 2D-NMR spectroscopy and CD spectroscopy, the hydrophilic Gly-containing peptides (Ac-TyrProGlyZaaVal-NH2; Zaa = Asp, Asn) were shown to exhibit a higher degree of beta-turn structure in solution than the Ile-containing peptides (Ac-TyrProIleZaaVal-NH2; Zaa = Asp, Asn). CD spectroscopy was used to show that the Gly-containing hydrophobic peptides (Ac-YaaProGlyIleVal-NH2; Yaa = Tyr; Phe: and Ac-PheProGlyIle-NH2) exhibited a higher degree of beta-turn structure in solution than the lie-containing hydrophobic peptides. The P-eff values of all four hydrophilic peptides across unperturbed Caco-2 cell monolayers were very low and no statistically significant differences were observed between the Gly-and lie-containing pentapeptides within either the Asp or Asn series. The P-eff values for the hydrophobic Gly-containing peptides were significantly greater than the P-eff values determined for their Lie-containing counterparts. The Gly-containing penta- and tetrapeptides in the Phe series, which exhibited high permeation, were shown to be metabolically unstable. In contrast, the Gly-and lie-containing pentapeptides in the Tyr series and the lie-containing penta-and tetrapeptides in the Phe series, which exhibited low permeation, were metabolically stable.Conclusions. Hydrophobic peptides that exhibit significant beta-turn structure in solution are more lipophilic as measured by log P-o/w and more readily permeate Caco-2 cell monolayers via the transcellular route than hydrophobic peptides that lack this type of solution structure. The ability of these peptides to permeate Caco-2 cell monolayers via the transcellular route also exposed them to metabolism, presumably by cytosolic endopeptidases. Similar secondary structural features in hydrophilic peptides do not appear to sufficiently alter the physicochemical properties of the peptides so as to alter their paracellular flux through unperturbed Caco-2 cell monolayers.