Thermodynamics of cyclophilin catalyzed peptidyl-prolyl isomerization by NMR spectroscopy.
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.
Videen
J S
JS
Department of Medicine, University of California at San Diego, La Jolla 92093.
Stamnes
M A
MA
Hsu
V L
VL
Goodman
M
M
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
D002352:Carrier Proteins; D011392:Proline; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase