Chemical modification of the histidine residues of purified hepatic cytochrome P-450: influence on substrate binding and the haemoprotein spin state.


A hepatic cytochrome P-450 isolated in an electrophoretically homogeneous form from phenobarbital-treated rats, exists predominantly in the low spin configuration (82% at 20 degrees C). The addition of saturating amounts of the substrate benzphetamine to this haemoprotein shifted the spin equilibrium to the high spin form, resulting in a doubling of the… (More)