title: Cis-trans isomerization of an angiotensin I-converting enzyme inhibitor. An enzyme kinetic and nuclear magnetic resonance study.
abstract: The angiotensin I-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) inhibitor, ramiprilat (2-[N-[(S)-1-ethoxycarbonyl-3-phenylpropyl]-L-Ala]-(1S,3S,5S)-2- azabicyclo[3.3.0]octane-3-carboxylic acid), is shown to exist in tow conformational isomers, cis and trans, which interconvert around the amide bond. The two conformers were separated by reversed-phase high-performance liquid chromatography. The conformers were identified by nuclear Overhauser effect measurements. From line shape analysis the isomerization rate constants were determined to be kcis----trans = 15 s-1 and ktrans----cis = 5 s-1 at 368 K in [2H]phosphate buffer (p2H 7.5). By enzyme kinetic studies using 3-(2-furylacryloyl)-L-Phe-Gly-Gly as substrate, the trans conformer was found to be the most potent enzyme inhibitor, whereas the cis conformer had a very low inhibitory effect. A new inhibition mechanism is presented for this type of slow, tight-binding inhibitors that contain an amide bond. This mechanism involves an equilibrium between the two conformers and the enzyme-bound inhibitor complex.
authors.affiliation: Department of Biochemistry and Biophysics, Chalmers University of Technology, Göteborg, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Skoglöf
authors.forename: I
authors.initials: I
authors.lastname: Nilsson
authors.forename: S
authors.initials: S
authors.lastname: Gustafsson
authors.forename: J
authors.initials: J
authors.lastname: Deinum
authors.forename: P O
authors.initials: PO
authors.lastname: Göthe
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000737:chemistry*; D004121:Dimethyl Sulfoxide; D007536:Isomerism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D011485:Protein Binding; D011758:Pyrroles / Q000737:chemistry* / Q000378:metabolism; D017257:Ramipril / Q000031:analogs & derivatives*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D011758:Pyrroles; C052549:ramiprilat; D007703:Peptidyl-Dipeptidase A; D017257:Ramipril; D004121:Dimethyl Sulfoxide