| Abstract: | Deuterium exchangeable hyperfine proton NMR resonances of cytochrome c peroxidase (EC 1.11.1.5) are identified in H2O solutions of the enzyme. One of these is assigned to the proximal histidine's imidazole N-H. Its shift and pH dependence indicate that an imidazolate form, which has been postulated for peroxidases, is ruled out for cytochrome c peroxidase-cyanide. A qualitative comparison of relative heme-pocket dynamics is also possible. When the bulk water resonance is irradiated with a continuous, but off acquisition, decoupler frequency the N-H resonance shows no intensity loss, indicating that saturation transfer between the proximal histidine and solvent water is either minimal, or extremely slow. |
