[Oxidative modification of cytochrome P-450 during its function. II. Study of the mechanism of cytochrome P-450 LM2 inactivation in a soluble reconstructed monooxygenase system].

Inactivation of cytochrome P-450 LM2 induced by hydrogen peroxide formed in the active site of the enzyme was studied. Catalase did not protect cytochrome P-450 LM2 from inactivation during its operation in a soluble reconstituted system. The hemoprotein inactivation in this system was found to depend on the ratio of hemo- to flavoproteins.

[Oxidative modification of cytochrome P-450 during its function. I. Comparative study of the inactivation of cytochrome P-450 LM2 in various systems].

The changes in the content of purified isolated cytochrome P-450 LM2 under the action of hydrogen peroxide and during its operation in a soluble reconstituted system were studied. It was found that cytochrome P-450 LM2 inactivation by hydrogen peroxide is accompanied by a decrease in the hemoprotein activity, loss of heme, oxidation of SH-groups and changes in the oligomeric state of the enzyme. There were some differences in the mechanisms of cytochrome P-450 LM2 inactivation under the action of H2O2 and during catalysis.

[Induction of cytochrome P-450 by triterpensaponins in Vietnamese ginseng].

It was found that rat liver cytochrome P-450 is induced by the Vietnamese ginseng triterpensaponines mixture (TSM) as well as by K5VN Panaxozides-11 (VP-11) purified from this mixture. Addition of TSM and VP-11 accelerates benz(alpha)pyrene and aminopyrine hydroxylation and increases the content of cytochrome P-450 isoforms with Mr of 57 kDa and 54 kDa in rat liver microsomes. Since VP-11 accounts for about 50% of TSM, the results obtained suggest that the microsomal monooxygenase system induction is caused by this triterpensaponine.

[The effect of phenobarbital and amidopyrine on the rate of decomposition of isoforms of cytochrome P-450 in mouse liver microsomes].

Separation of microsomal proteins in gradient polyacrylamide gel gives 60 protein bands. The molecular mass range of 48-58 kDa corresponding to cytochrome isozymes contains 7 bands for intact mice and 8 bands for phenobarbital-induced mice. Phenobarbital treatment causes both the appearance of a new cytochrome P-450 isozyme with a molecular mass of 56 kDa and the increase in the content of three isozymes with molecular masses of 54, 52.

[Rate of microsomal protein metabolism in the mouse liver].

NaH14CO3, a poorly reutilized biosynthesis precursor, was used to study the rate of whole microsomal protein degradation in mouse liver. The use of the precursors, however, does not prevent the reutilization of labeled amino acids on phenobarbital administration. To avoid reutilization, a new method has been developed.