Enzymatic activities of matrix-bound components of the liver microsomal cytochrome P-450 system.

Cytochrome P-450 and NADPH-cytochrome P-450 reductase were covalently attached to Sepharose 4B in different ways in order to find out factors which are important for the organization of the individual components to a catalytically active system. Both proteins can be bound individually, simultaneously, and successively to the matrix retaining N-demethylase activity after reconstitution with the complementary essential components. The activity of the system with immobilized components depends on the individual component, the sequence of fixation if both proteins are bound, the degree of purification, and the level of disintegration (detergent-treated samples). The functional importance of the lipid component is beyond doubt, but its specific role needs further investigations. At present it is difficult to differentiate between the influence of chemical modification on the properties of the proteins and the disturbed interactions within the system as the main reason for the decrease in the activity after immobilization. The cluster-like (aggregated) arrangement of the cytochrome P-450 system is necessary for an optimal activity.