Human Carboxymethylenebutenolidase as a Bioactivating Hydrolase of Olmesartan Medoxomil in Liver and Intestine

• Published in: The Journal of biological chemistry Vol. 285; no. 16; pp. 11892 - 11902
• Main Authors: Ishizuka, Tomoko, Fujimori, Izumi, Kato, Mitsunori, Noji-Sakikawa, Chisa, Saito, Motoko, Yoshigae, Yasushi, Kubota, Kazuishi, Kurihara, Atsushi, Izumi, Takashi, Ikeda, Toshihiko, Okazaki, Osamu
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16-04-2010; American Society for Biochemistry and Molecular Biology
• Subjects: Activation; Amino Acid Sequence; Angiotensin II Type 1 Receptor Blockers - pharmacokinetics; Biotransformation; Carboxylic Ester Hydrolases - antagonists & inhibitors; Carboxylic Ester Hydrolases - genetics; Carboxylic Ester Hydrolases - isolation & purification; Carboxylic Ester Hydrolases - metabolism; Cell Line; CMBL; Cytosol - enzymology; DNA Primers - genetics; Enzyme Inhibitors - pharmacology; Enzymes; Enzymology; Esterase; Female; Humans; Identification; Imidazoles - chemistry; Imidazoles - pharmacokinetics; In Vitro Techniques; Intestines - enzymology; Kinetics; Liver - enzymology; Male; Metabolism/Drug; Molecular Sequence Data; Mutagenesis, Site-Directed; Olmesartan Medoxomil; Pregnancy; Prodrug; Prodrugs - chemistry; Prodrugs - pharmacokinetics; Protein/Purification; Pseudomonas; Recombinant Proteins - antagonists & inhibitors; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; Site-directed Mutagenesis; Tetrazoles - chemistry; Tetrazoles - pharmacokinetics; Tissue Distribution; Xenobiotics; Site-directed Mutagenesis; Enzymes; Esterase; Metabolism/Drug; Protein/Purification; Activation; Identification; CMBL; Prodrug; Xenobiotics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.072629

Olmesartan medoxomil (OM) is a prodrug type angiotensin II type 1 receptor antagonist widely prescribed as an antihypertensive agent. Herein, we describe the identification and characterization of the OM bioactivating enzyme that hydrolyzes the prodrug and converts to its pharmacologically active metabolite olmesartan in human liver and intestine. The protein was purified from human liver cytosol by successive column chromatography and was identified by mass spectrometry to be a carboxymethylenebutenolidase (CMBL) homolog. Human CMBL, whose endogenous function has still not been reported, is a human homolog of Pseudomonas dienelactone hydrolase involved in the bacterial halocatechol degradation pathway. The ubiquitous expression of human CMBL gene transcript in various tissues was observed. The recombinant human CMBL expressed in mammalian cells was clearly shown to activate OM. By comparing the enzyme kinetics and chemical inhibition properties between the recombinant protein and human tissue preparations, CMBL was demonstrated to be the primary OM bioactivating enzyme in the liver and intestine. The recombinant CMBL also converted other prodrugs having the same ester structure as OM, faropenem medoxomil and lenampicillin, to their active metabolites. CMBL exhibited a unique sensitivity to chemical inhibitors, thus, being distinguishable from other known esterases. Site-directed mutagenesis on the putative active residue Cys132 of the recombinant CMBL caused a drastic reduction of the OM-hydrolyzing activity. We report for the first time that CMBL serves as a key enzyme in the bioactivation of OM, hydrolyzing the ester bond of the prodrug type xenobiotics.