title: Kinetics of elementary steps in the cytochrome P-450 reaction sequence. III. NADPH reduction of cytochrome P-450LM at different integrational levels.
abstract: The aerobic NADPH reduction of cytochrome P-450LM has been investigated on microsomes, as well as on the solubilized enzyme system in the associated, disintegrated, and reconstituted state, respectively. P-450 exhibits biphasic reduction kinetics of about 70/30% phase distribution and rate constants differing 10-fold. The partial reactions are due to organizational asymmetries, the cytochrome being either incorporated into P-450/reductase associates (cluster) or localized outside (randomly distributed, homoassociated, weakly cluster-associated). Triton N-101 disintegrates the different associate structures, consequently followed by the disappearance of the rapid reaction phase. The enzyme system can be reconstituted; at microsomal stoichiometry the respective standard parameters are approached, depending on the composition and structural organization of the phospholipid. The reorganization without any membrane matrix is obviously thermodynamically determined.
mesh_terms: D000818:Animals; D001589:Benzphetamine; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism*; D009249:NADP; D010084:Oxidation-Reduction; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D011817:Rabbits; D012995:Solubility
chemical_list: D001589:Benzphetamine; D011092:Polyethylene Glycols; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D010089:Oxidoreductases, N-Demethylating