Hydrolysis of angiotensin II receptor blocker prodrug olmesartan medoxomil by human serum albumin and identification of its catalytic active sites
Hydrolysis of angiotensin II receptor blocker prodrug olmesartan medoxomil by human serum albumin and identification of its catalytic active sites
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DOI：
10.1124/dmd.105.006163
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发表时间：
2005-12-01
影响因子：
3.9
通讯作者：
Otagiri, M
中科院分区：
文献类型：
--
作者：
Ma, SF;Anraku, M;Otagiri, M
在本研究中，我们研究了人血清白蛋白（HSA）的酯酶样活性及其水解机制，从而激活奥美沙坦酯（CS-866），一种新的血管紧张素II受体拮抗剂。CS-866先前已显示在血清中快速水解，其中HSA似乎在催化水解中发挥最重要的作用。结果表明，CS-866的水解遵循米氏动力学。与对硝基苯酚乙酸酯（PNPA）释放对硝基苯酚相比，CS-866对HSA的亲和力较低，催化水解速率较低。热力学数据表明，PNPA具有比CS-866更小的活化熵值（Δ S）;因此，PNPA比CS-866更具反应性。依那普利和华法林作为CS-866水解的竞争性抑制剂，而丹磺酰-L-天冬酰胺、对氨基苯甲酸正丁酯和地西泮则没有。这些发现表明，水解活性与部分位点I和位点II的配体结合。所有化学修饰的HSA衍生物（Tyr-、Lys-、His-和Trp-修饰）具有比天然HSA显著更低的反应性; Lys-HSA和Trp-HSA具有特别低的反应性。所有测试的突变体HSA（K199 A、W214 A和Y 411 A）均表现出反应性的显著降低，表明Lys-199、Trp-214和Tyr-411在水解中起重要作用。利用计算机对接模型得到的结果与实验结果一致，并有力地支持了我们从实验中得出的假设。
In the present study, we investigated the esterase-like activity of human serum albumin (HSA) and the mechanism by which it hydrolyzes, and thereby activates, olmesartan medoxomil (CS-866), a novel angiotensin II receptor antagonist. CS-866 has previously been shown to be rapidly hydrolyzed in serum in which HSA appeared to play the most important role in catalyzing the hydrolysis. We found that the hydrolysis of CS-866 by HSA followed Michaelis-Menten kinetics. Compared with the release of p-nitrophenol from p-nitrophenyl acetate (PNPA), CS-866 showed lower affinity to HSA and a lower catalytic rate of hydrolysis. Thermodynamic data indicated that PNPA has a smaller value of activation entropy (Delta S) than CS-866; consequently, PNPA is more reactive than CS-866. Ibuprofen and warfarin acted as competitive inhibitors of hydrolysis of CS-866, whereas dansyl-L-asparagine, n-butyl p-aminobenzoate, and diazepam did not. These findings suggest that the hydrolytic activity is associated to parts of site I and site II for ligand binding. All chemically modified HSA derivatives (Tyr-, Lys-, His-, and Trp-modifications) had significantly lower reactivity than native HSA; Lys- HSA and Trp-HSA had especially low reactivity. All the mutant HSAs tested (K199A, W214A, and Y411A) exhibited a significant decrease in reactivity, suggesting that Lys-199, Trp-214, and Tyr-411 play important roles in the hydrolysis. Results obtained using a computer docking model are in agreement with the experimental results, and strongly support the hypotheses that we derived from the experiments.