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The dynamics of the inductive effects of MC and TCDD upon rat liver microsomal benzpyrene hydroxylase and the main properties of the de novo synthesized hemoproteins have been compared. The inadequacy of expression of the enzyme activity per total cytochrome P-448 content has been established. It was concluded that TCDD microsomes have a relatively low content of benzpyrene hydroxylase with a higher molecular activity than the enzyme from MC microsomes.

Longitudinal relaxation (T1) measurements for all lines (alpha-CH, beta-CH, O-CH3) in the 4-methoxypyridine 1H-NMR spectrum were used to study the interaction of 4-methoxypyridine with purified microsomal cytochrome P-450 from livers of phenobarbital-treated rats. The paramagnetic contribution to the observed T1(-1) value was determined from its dependence on 4-methoxypyridine concentration. In the P-450-4-methoxypyridine complex the latter is oriented so that the nitrogen of pyridine is directed towards the Fe3+.

The benzopyrene hydroxylase activity of the methylcholanthrene-inducible form of cytochrome P-450 (P-448) has been studied in native and reconstituted liver microsomal membranes. The data obtained show that the molecular catalytic activity of membrane-bound cytochrome P-448 depends on the molar ratio of the cytochrome to NADPH-cytochrome P-450 reductase and that the optimal ratio for maximal activity of cytochrome P-448 in the microsomal membrane essentially differs from the equimolar one.

Longitudinal relaxation (T1) measurements for all lines (N(CH3)2, N(CH3), C(CH3), phenyl) in the aminopyrine 1H-NMR spectrum were used to study the interaction of aminopyrine with purified microsomal cytochrome P-450 from livers of phenobarbital-treated rats. The paramagnetic contribution to the observed T1(-1) values was determined from its dependence on aminopyrine concentration. The Solomon-Bloembergen equation was used to calculate between Fe3+ and aminopyrine distances in the enzyme-substrate complex. For all protons these distances are about 8 A.