[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.

[Isolation and properties of cytochrome P-450 from rabbit liver microsomes].

A purified low-spin form of cytochrome P-450 was isolated from phenobarbital-induced rabbit liver microsomes. The preparation was functionally active and free from cytochromes b5 and P-420 and phospholipids. The specific content of the cytochrome was 18 nmoles per mg of protein.

The properties of cytochrome P-450 and hydroxylase activity of reconstituted proteoliposomal membranes.

Type I substrates are bound to soluble cytochrome P-450 worse than to microsomes. The incorporation of haemoprotein into phosphatidylcholine liposomes restores the capability of isolated cytochrome P-450 to interact with such substrates as well as the microsomal form. The soluble and lipid-binding cytochrome P-450 does not differ in its thermal stability and protease digestion.