title: Thermodynamics of cyclophilin catalyzed peptidyl-prolyl isomerization by NMR spectroscopy.
abstract: One-dimensional nmr exchange spectroscopy was carried out to determine thermodynamic parameters of cyclophilin-induced cis-trans isomerization of succinyl-Ala-Phe-Pro-Phe-p-nitroanilide. Rate measurements were possible at physiological temperatures. The kc/Km of rat cyclophilin was found to be 12.8 (+/- 0.5) s-1 microM-1 at 37 degrees C, intermediate to previously reported values that used a coupled enzyme assay extrapolated to this temperature. Activation energies (delta G not equal to) for the uncatalyzed and catalyzed reaction at 37 degrees C were found to be 19.7 and 17.1 kcal/mol, respectively, and were primarily due to an enthalpic barrier.
authors.affiliation: Department of Medicine, University of California at San Diego, La Jolla 92093.
authors.forename: J S
authors.initials: JS
authors.lastname: Videen
authors.forename: M A
authors.initials: MA
authors.lastname: Stamnes
authors.forename: V L
authors.initials: VL
authors.lastname: Hsu
authors.forename: M
authors.initials: M
authors.lastname: Goodman
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry*; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D002384:Catalysis; D007536:Isomerism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase; D011392:Proline / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002352:Carrier Proteins; D011392:Proline; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase