Valenta Claudia, Marschütz Michaela, Egyed Christiane, Bernkop-Schnürch Andreas
Institute of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Austria.
J Pharm Pharmacol. 2002 May;54(5):603-10. doi: 10.1211/0022357021778907.
The purpose of this study was to evaluate the inhibitory effect of thiolated carbopol 974P (carb-cys) on the enzymatic activity of vaginal aminopeptidase N in-vitro. Mediated by a carbodiimide, L-cysteine was covalently linked to carbopol 974P. Depending on the weight ratio of polymer to cysteine during the coupling reaction, resulting conjugates displayed 31.3-54.4 micromol thiol groups per g polymer. The inhibitory effect of carb-cys conjugates was evaluated towards isolated aminopeptidase N and aminopeptidase-N-like activity of excised vaginal mucosa covered with native mucus, respectively. Enzymatic activity was assayed spectrophotometrically using L-leucine-p-nitroanilide (L-leu-pNA) as a synthetic substrate. Carb-cys thereby showed a significantly higher inhibitory effect than unmodified polymer towards both isolated enzyme and vaginal mucosa. Moreover, enzyme inhibition was strongly dependent on the amount of thiol groups being immobilised. The more thiol groups available the higher was the inhibitory effect. Due to its additional high cohesive properties and the possibility of a sustained drug release, which could be shown for the model drug LH-RH, carb-cys appears interesting for the development of vaginal peptide drug-delivery systems.
本研究的目的是在体外评估硫醇化卡波姆974P（carb-cys）对阴道氨肽酶N酶活性的抑制作用。在碳二亚胺的介导下，L-半胱氨酸与卡波姆974P共价连接。根据偶联反应过程中聚合物与半胱氨酸的重量比，所得共轭物每克聚合物显示出31.3 - 54.4微摩尔的硫醇基团。分别评估了carb-cys共轭物对分离的氨肽酶N和覆盖有天然黏液的离体阴道黏膜的氨肽酶N样活性的抑制作用。使用L-亮氨酸-对硝基苯胺（L-leu-pNA）作为合成底物，通过分光光度法测定酶活性。由此可见，carb-cys对分离的酶和阴道黏膜均显示出比未修饰聚合物更高的抑制作用。此外，酶抑制作用强烈依赖于固定化的硫醇基团数量。可用的硫醇基团越多，抑制作用越强。由于其具有额外的高黏附特性以及模型药物促性腺激素释放激素（LH-RH）所显示的持续药物释放可能性，carb-cys对于阴道肽药物递送系统的开发似乎很有意义。
