[Inactivation of cytochrome P-450 by hydrogen peroxide formed in the catalytic cycle during peroxy-complex degradation].

It was shown that the crucial role in the inactivation of microsomal cytochrome P-450 in reactions of hydroxylation of type I (DMA, AP, BPh, p-NA) and type II (AN) substrates belongs to H2O2 directly formed in the enzyme active center during the decomposition of the peroxy complex. Hydrogen peroxide formed via an indirect pathway during the dismutation of superoxide radicals does not play a role in the hemoprotein inactivation.

[Effect of monooxygenase reactions catalyzed by cytochrome P-450 on the microsomal membrane].

Hydroxylation of dimethylaniline in rabbit liver microsomes is accompanied by inactivation of cytochrome P-450 and the formation of products inhibiting the catalytic activity of non-inactivated cytochrome P-450. Other enzymes and electron carriers of microsomal membrane (cytochrome b5, NADH-ferricyanide reductase, NADPH-cytochrome c and NADPH-cytochrome P-450 reductases) as well as glucose-6-phosphatase were not inactivated in the course of the monooxygenase reactions. Phospholipids and microsomal membrane proteins were also unaffected thereby.

[Induction of cytochrome P-450 and the immune response by free and covalently bound to albumin phenobarbital].

There is a relationship between the induction of microsomal enzymes and xenobiotic-induced immunological response. Phenobarbital bound with albumin covalently loses the ability to induce the cytochrome P 450-hydroxylase system but acquires an ability to induce the lymphocytic immunological system. This indicates that the two protection systems of the body, hydroxylase and immune ones, can interact with low and high molecular xenobiotics.

[Effect of purified cytochrome P450 incorporation into liposomal membranes on its properties].

The physico-chemical properties and hydroxylase activity of three forms of cytochrome P450, i. e. purified soluble hemoprotein, purified hemoprotein incorporated into the liposomal membrane and microsomal cytochrome P450, were studied.