QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: dmd.105.006163v1 33/12/1911    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ma, S.-F. Articles by Otagiri, M. Search for Related Content PubMed PubMed Citation Articles by Ma, S.-F. Articles by Otagiri, M.

HYDROLYSIS OF ANGIOTENSIN II RECEPTOR BLOCKER PRODRUG OLMESARTAN MEDOXOMIL BY HUMAN SERUM ALBUMIN AND IDENTIFICATION OF ITS CATALYTIC ACTIVE SITES

Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan (S.-F.M., M.A., Y.I., M.O.); Department of Pharmacy, Miyazaki Medical College Hospital, Miyazaki, Japan (K.Y.); Department of Medical Biochemistry, University of Aarhus, Aarhus, Denmark (U.K.-H.); the School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan (N.Y., S.H.); and Drug Metabolism and Pharmacokinetics Research Laboratories, Sankyo Co., Ltd., Tokyo, Japan (T.I.)

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 (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.