title: Stereoselective inhibition of human butyrylcholinesterase by the enantiomers of bambuterol and their intermediates.
abstract: This work describes the sequential hydrolysis of bambuterol enantiomers and their monocarbamate metabolites (MONO) catalyzed by human butyrylcholinesterase (BChE) as well as the enzyme inhibition resulting from this process. Particular emphasis is given to the contribution given by MONO to the enzyme inhibition because it was not fully characterized in previous works. Bambuterol and MONO enantiomers displayed the same time- and concentration-dependent mechanism of interaction with the enzyme. The hydrolysis kinetics of both bambuterol and MONO was enantioselective, and the (R)-enantiomer of each compound was hydrolyzed fourfold faster than the respective (S)-enantiomer. Even though the enzyme inhibition rates of (R)- and (S)-MONO were much slower than those of their respective bambuterol enantiomers (∼15-fold), both MONO enantiomers showed a significant BChE inhibition when physiologically relevant concentrations of enzyme and inhibitors were used (∼50% of their respective bambuterol enantiomers). The kinetic constants obtained by testing each single compound were used to model the contribution given by MONO to the enzyme inhibition observed for bambuterol. The hydrolysis of MONO enantiomers enhanced the inhibitory power of bambuterol enantiomers of about 27.5% (R) and 12.5% (S) and extended more than 1 hour the duration of inhibition. The data indicate that MONO contribute significantly to the inhibition of BChE occurring in humans upon administration of normal doses of bambuterol. In addition, the hydrolysis of MONO resulted in the rate-limiting step in the conversion of bambuterol in its pharmacologically active metabolite terbutaline; therefore, MONO concentrations should always be monitored during pharmacokinetic studies of bambuterol.
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Higher Education Mega Center, Guangzhou, People's Republic of China (M.P., H.D., H.W., W.T.); Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, People's Republic of China (M.P., H.D., H.W.); and Key Laboratory of Industrial Biotechnology of Guangdong Higher Education Institutes, South China University of Technology, Guangzhou, People's Republic of China (M.P., W.T.).
authors.forename: Marco
authors.initials: M
authors.lastname: Pistolozzi
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Higher Education Mega Center, Guangzhou, People's Republic of China (M.P., H.D., H.W., W.T.); Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, People's Republic of China (M.P., H.D., H.W.); and Key Laboratory of Industrial Biotechnology of Guangdong Higher Education Institutes, South China University of Technology, Guangzhou, People's Republic of China (M.P., W.T.).
authors.forename: Huaqiao
authors.initials: H
authors.lastname: Du
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Higher Education Mega Center, Guangzhou, People's Republic of China (M.P., H.D., H.W., W.T.); Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, People's Republic of China (M.P., H.D., H.W.); and Key Laboratory of Industrial Biotechnology of Guangdong Higher Education Institutes, South China University of Technology, Guangzhou, People's Republic of China (M.P., W.T.).
authors.forename: Hong
authors.initials: H
authors.lastname: Wei
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Higher Education Mega Center, Guangzhou, People's Republic of China (M.P., H.D., H.W., W.T.); Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, People's Republic of China (M.P., H.D., H.W.); and Key Laboratory of Industrial Biotechnology of Guangdong Higher Education Institutes, South China University of Technology, Guangzhou, People's Republic of China (M.P., W.T.) went@scut.edu.cn.
authors.forename: Wen
authors.initials: W
authors.lastname: Tan
mesh_terms: D002091:Butyrylcholinesterase / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D013237:Stereoisomerism; D013726:Terbutaline / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D002800:Cholinesterase Inhibitors; D002091:Butyrylcholinesterase; D013726:Terbutaline; C047766:bambuterol