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Inactivation rate of purified oligomeric cytochrome P-450 LM2 has been investigated in glucose oxidase system and under the action of exogenous hydrogen peroxide (400 microM). It has been found that hydrogen peroxide has a distinct inactivating effect on cytochrome P-450. The enzyme inactivation is accompanied by the loss of heme and the decrease in SH-group content in the protein molecule. Benzphetamine, a substrate specific for this enzyme isoform, exerts a protective effect by decreasing the rate of cytochrome P-450 inactivation and SH-group oxidation. Similar results have been obtained during the investigation of cytochrome P-450 inactivation in the monomerized system. It has been found that the inactivation process is accompanied by the formation of the enzyme aggregates. The changes in the aggregate state are due to the formation of intermolecular covalent bonds.

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. The cytochrome P 450-hydroxylase system of the liver and other tissues is intended for protection of the body from the action of low molecular hydrophobic compounds. The immunological system is responsible for the organism protection from high molecular compounds.