title: Spin transition of camphor-bound cytochrome P-450. 1. local paH and electrostatic interactions.
abstract: Variations of the spin state in camphor-bound cytochrome P-450 are interpreted in the light of the polyelectrolyte theory and its implications on the microenvironment of the heme. The ratio of high-spin to low-spin iron can serve as a tool to determine the local paH in the microenvironment of a group (pK0, app approximately 5.4) which governs the spin state. The local paH depends on the electrostatic potential created by negatively charged groups (pKa = 5.6), modulated in turn by paH and by the screening effect of ionic strength. A model is given for the proton-coupled spin state change.
mesh_terms: D002164:Camphor; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008433:Mathematics; D009994:Osmolar Concentration; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D002164:Camphor; D003577:Cytochrome P-450 Enzyme System