Kinetics of elementary steps in the cytochrome P-450 reaction sequence. III. NADPH reduction of cytochrome P-450LM at different integrational levels
Blanck, J.; Behlke, J.; Jänig, G.R.; Pfeil, D.; Ruckpaul, K.
Acta Biologica et Medica Germanica 38(1): 11-21
1979
ISSN/ISBN: 0001-5318 PMID: 42245 Document Number: 151831
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.