I. B. Tsyrlov

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The inhibitory and stimulatory effects of six flavonoids with distinct hydroxylation patterns on the recombinant and hepatic mouse and human CYP1A P-450s were studied. cDNA-expressed mouse CYP1A1 and CYP1A2 differed in their sensitivity to both hydroxylated and nonhydroxylated flavonoids, respectively. A comparison between the mouse and human CYP1A2(More)
Kinetics of benzo[alpha]pyrene hydroxylase (AHH), 7-methoxyresorufin o-demethylase (MROD), and 7-ethoxyresorufin o-deethylase (EROD) were estimated in microsomes of Hep G2 cells infected with a recombinant vaccinia virus bearing mouse CYP1A1 or CYP1A2 cDNAs. The kcat and Km values obtained were compared with those of liver microsomal and purified mouse(More)
The microsomal ethanol oxidizing system comprises an ethanol-inducible cytochrome P-4502E1, but the involvement of other P-450s has also been suggested. In our study, human CYP2E1, CYP1A2, and CYP3A4 were heterologously expressed in HepG2 cells, and their ethanol oxidation was assessed using a corresponding selective inhibitor: all three P-450 isoenzymes(More)
BACKGROUND Recently, we showed that, in addition to cytochrome P-4502E1 (CYP2E1), CYP1A2 and CYP3A4 also contribute to the microsomal ethanol oxidizing system (MEOS). When MEOS activity is measured, sodium azide commonly is used to block the contaminating catalase. However, although CYP2E1 is considered insensitive to azide, its effect on the other P-450s(More)
Porphyria cutanea tarda is associated with excess hepatic production of uroporphyrin. Oxidation of uroporphyrinogen to uroporphyrin was previously demonstrated to be specifically catalyzed by cytochrome P450 (CYP) 1A2. Here, we investigated the ability of human CYP1A2 to catalyze uroporphyrinogen oxidation (UROX). UROX activity in human liver microsomes was(More)
A form of cytochrome P-450 (P-450PB) with a molecular weight of 53.5-54.0 kD possessing a high benzphetamine-N-demethylase activity (100-120 nmol formaldehyde/min/nmol cytochrome) was isolated from liver microsomes of phenobarbital-induced C57Bl/6 mice. This cytochrome P-450 form is immunologically identical to its rat liver counterpart-P-450b (Mr = 52 kD)(More)
A study has been made of a model of "consecutive" induction of microsomal monooxygenases following treatment with phenobarbital which was administered after maximal induction by 3-methylcholanthrene. It has been found that in this "consecutive" system, notwithstanding the discontinuation of 3-methylcholanthrene, phenobarbital stimulates the further(More)
Phenoxyl radicals are intermediates of one-electron oxidation of phenolic compounds by various peroxidases. This report describes reactions of phenoxyl radicals with human NADPH-cytochrome P-450 oxidoreductase (OR) and NADPH. Purified truncated OR catalyzed quenching of EPR signal of the phenoxyl radical of a vitamin E homolog,(More)
1. Treatment of liver microsomal fraction with 0.03-0.12% sodium deoxycholate and 0.005-0.06 mM carbonyl cyanide m-chlorophenylhydrazone decreases phospholipid-dependent hydrophobicity of the microsomal membrane, assayed by the kinetics of 8-anilinonaphthalene-1-sulphonate binding and ethyl isocyanide difference spectra. 2. Sodium deoxycholate at a(More)