Effects of acetylenic and olefinic pyrenes upon cytochrome P-450 dependent benzo[a]pyrene hydroxylase activity in liver microsomes

1985 ◽  
Vol 129 (2) ◽  
pp. 591-596 ◽  
Author(s):  
Liang-Shang L. Gan ◽  
Jui-Yun L. Lu ◽  
Douglas M. Hershkowitz ◽  
William L. Alworth
Keyword(s):  
Liver Microsomes ◽  
Hydroxylase Activity ◽  
Pyrene Hydroxylase ◽  
Cytochrome P 450

1-Ethynylpyrene, a suicide inhibitor of cytochrome P-450 dependent benzo[a]pyrene hydroxylase activity in liver microsomes

Biochemistry ◽  
1984 ◽  
Vol 23 (17) ◽  
pp. 3827-3836 ◽  
Author(s):  
Liang Shang L. Gan ◽  
Abelardo L. Acebo ◽  
William L. Alworth
Keyword(s):  
Liver Microsomes ◽  
Hydroxylase Activity ◽  
Pyrene Hydroxylase ◽  
Cytochrome P 450

scholarly journals Identification of the human liver cytochrome P-450 responsible for coumarin 7-hydroxylase activity

1990 ◽  
Vol 267 (2) ◽  
pp. 365-371 ◽  
Author(s):  
J S Miles ◽  
A W McLaren ◽  
L M Forrester ◽  
M J Glancey ◽  
M A Lang ◽  
...  
Keyword(s):  
Human Liver ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Hydroxylase Activity ◽  
Liver Cytochrome ◽  
Partial Length ◽  
Coumarin 7 ◽  
Human Livers ◽  
Cell Expression ◽  
Cytochrome P 450

1. We have constructed a full-length human liver cytochrome P450IIA cDNA from a partial-length clone by oligonucleotide-directed mutagenesis, and subcloned it into the monkey kidney (COS-7) cell expression vector, pSVL. 2. The cDNA encodes a 49 kDa protein with coumarin 7-hydroxylase (COH) activity which cross-reacts with antisera to the mouse cytochrome P-450 isoenzyme responsible for COH activity and comigrates with a human liver microsomal protein. 3. Western blot analysis of a panel of human livers indicates that the level of the 49 kDa protein, detected using antisera to either the mouse COH P-450 or rat P450IIA1 protein, correlates very highly with COH activity. 4. Antisera to the rat P450IIA1 protein can inhibit COH activity in human liver microsomes. Taken together, these data indicate that a member of the P450IIA subfamily is responsible for most, if not all, of the COH activity in human liver.

IN-VITRO METABOLISM OF 4-ANDROSTENE-3,17-DIONE BY HEPATIC MICROSOMES FROM THE RAINBOW TROUT (SALMO GAIRDNERII): EFFECTS OF HYPOPHYSECTOMY AND OESTRADIOL-17β

1981 ◽  
Vol 90 (1) ◽  
pp. 103-112 ◽  
Author(s):  
TIIU HANSSON ◽  
JAN-ÅKE GUSTAFSSON
Keyword(s):  
Rainbow Trout ◽  
Liver Microsomes ◽  
The Other ◽  
Sham Operation ◽  
Hydroxylase Activity ◽  
Oxidoreductase Activity ◽  
Hepatic Microsomes ◽  
Cytochrome P 450 ◽  
Reductive Metabolism

The metabolism of 4-androstene-3,17-dione by liver microsomes from juvenile rainbow trout, Salmo gairdnerii, was studied in vitro. Hypophysectomy of the fish significantly increased mean hepatic 17-hydroxysteroid oxidoreductase activity when compared with that from sham-operated fish but none of the other enzyme activities investigated were affected. Administration of oestradiol-17β resulted in a significant decrease in mean hepatic 6β-hydroxylase activity and total cytochrome P-450 content but had no effect on the 16-hydroxylation or on the reductive metabolism of androstenedione. The effect of oestradiol-17β on hepatic 6β-hydroxylase activity was as pronounced after hypophysectomy as after sham-operation indicating that these effects of oestradiol-17β are mainly direct and independent of the pituitary gland. The results indicate that hypophysial hormone(s) as well as oestradiol-17β play a role in the regulation of hepatic steroid metabolism in trout.

Modulation of Microsomal Cytochrome P450 by Scutellariae Radix and Gentianae Scabrae Radix in Rat Liver

1996 ◽  
Vol 24 (01) ◽  
pp. 19-29 ◽  
Author(s):  
Jaw-Jou Kang ◽  
Yi-Chien Chen ◽  
Wei-Chung Kuo ◽  
Terri Chen ◽  
Yu-Wen Cheng ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Medicinal Herbs ◽  
Hydroxylase Activity ◽  
Microsomal Cytochrome ◽  
Aniline Hydroxylase ◽  
Scutellariae Radix ◽  
Microsomal Cytochrome P450 ◽  
Pyrene Hydroxylase

The present study has determined the effects of Scutellariae Radix (Huangqin) and Gentianae scabrae Radix (Longdan) on liver microsomal cytochrome P450 (P450)-dependent mono-oxygenases using rats pretreated with crude extracts of medicinal herbs. Scutellariae Radix resulted in a 53% decrease of pentoxyresorufin O-dealkylase activity in liver microsomes. In contrast, Gentianae scabrae Radix caused a 50% increase of benzo(a)pyrene hydroxylase activity. Immunoblotting 1A and 2B proteins, respectively. Scutellariae and Gentianae scabrae Radixes had no effects on microsomal aniline hydroxylase activity and P450 2E1 protein.

The characteristics of the microsomal hydroxylation of tolbutamide

1991 ◽  
Vol 69 (3) ◽  
pp. 400-405 ◽  
Author(s):  
Pierre M. Bélanger ◽  
Serge St-Hilaire
Keyword(s):  
Carbon Monoxide ◽  
Liver Microsomes ◽  
Hepatic Metabolism ◽  
Species Variation ◽  
Rat Liver Microsomes ◽  
Hydroxylase Activity ◽  
Microsomal Metabolism ◽  
Microsomal Hydroxylation ◽  
Cytochrome P 450

The in vitro metabolism of tolbutamide to the hydroxymethyl derivative was studied using hepatic microsomal homogenates. The hydroxymethyl metabolite was quantitated by HPLC. The hepatic microsomal hydroxylase was completely inhibited by carbon monoxide and was NADPH dependent. Metyrapone, α-naphthoflavone, phenelzine, mercuric chloride, and nitrogen significantly inhibited the reaction indicating the involvement of the cytochrome P-450 monooxygenase. Species variation showed that the order of hepatic microsomal activity was rat > rabbit >> guinea pig >> mouse and hamster. The reaction increased with time up to 40 min and followed Michaelis–Menten kinetics in rat liver microsomes with apparent Km and Vmax values of 224.4 μM and 359.9 pmol∙mg−1∙min−1, respectively. The reaction was induced by phenobarbital but was depressed after pretreatment with 3-methylcholanthrene and isosafrole. However, expression of the hydroxylase activity per nanomoles of cytochrome P-450 showed that the activity was much higher in liver microsomes of isosafrole pretreated rats. These results indicate the involvement of different isozymes of cytochrome P-450 in the microsomal hydroxylation of tolbutamide.Key words: tolbutamide metabolism, tolbutamide hydroxylation, microsomal hydroxylation, microsomal metabolism of tolbutamide, hepatic metabolism of tolbutamide.

scholarly journals Androgen hydroxylation catalysed by a cell line (SD1) that stably expresses rat hepatic cytochrome P-450 PB-4 (IIB1)

1989 ◽  
Vol 260 (1) ◽  
pp. 81-85 ◽  
Author(s):  
D J Waxman ◽  
D P Lapenson ◽  
J J Morrissey ◽  
S S Park ◽  
H V Gelboin ◽  
...  
Keyword(s):  
Cell Line ◽  
Gene Product ◽  
Rat Liver ◽  
Membrane Fraction ◽  
Liver Microsomes ◽  
Parental Cell Line ◽  
Rat Liver Microsomes ◽  
Hydroxylase Activity ◽  
Specific Content ◽  
Cytochrome P 450

Androgen hydroxylation catalysed by Chinese hamster fibroblast SD1 cells, which stably express cytochrome P-450 form PB-4, the rat P450IIB1 gene product, was assessed and compared to that catalysed by purified cytochrome P-450 PB-4 isolated from rat liver. SD1 cell homogenates catalysed the NADPH-dependent hydroxylation of androstenedione and testosterone with a regioselectivity very similar to that purified by P-450 PB-4 (16 beta-hydroxylation/16 alpha-hydroxylation = 6.0-6.8 for androstenedione; 16 beta/16 alpha = 0.9 for testosterone). Homogenates prepared from the parental cell line V79, which does not express detectable levels of P-450 PB-4 or any other cytochrome P-450, exhibited no androgen 16 beta- or 16 alpha-hydroxylase activity. The hydroxylase activities catalysed by the SD1 cell homogenate were selectively and quantitatively inhibited (greater than 90%) by a monoclonal antibody to P-450 PB-4 at a level of antibody (40 pmol of antibody binding sites/mg of SD1 homogenate) that closely corresponds to the P-450 PB-4 content of the cells (48 pmol of PB-4/mg of SD1 homogenate). Fractionation of cell homogenates into cytosol and microsomes revealed that the P-450 PB-4-mediated activities are associated with the membrane fraction. Although the P-450 PB-4-specific content of the SD1 microsomes was 15% of that present in phenobarbital-induced rat liver microsomes, the P-450 PB-4-dependent androstenedione 16 beta-hydroxylase activity of the SD1 membrane fraction was only 2-3% of that present in the liver microsomes. This activity could be stimulated several-fold, however, by supplementation of SD1 microsomes with purified rat NADPH P-450 reductase. These studies establish that a single P-450 gene product (IIB1) can account for the hydroxylation of androgen substrates at multiple sites, and suggest that SD1 cells can be used to assess the catalytic specificity of P-450 PB-4 with other substrates as well.

scholarly journals Characterization of pig kidney microsomal cytochrome P-450 catalysing 25-hydroxylation of vitamin D3 and C27 steroids

1990 ◽  
Vol 270 (2) ◽  
pp. 345-350 ◽  
Author(s):  
T Bergman ◽  
H Postlind
Keyword(s):  
Vitamin D3 ◽  
Lauric Acid ◽  
Liver Microsomes ◽  
Hydroxylase Activity ◽  
Pig Liver ◽  
Pig Kidney ◽  
Sds Page ◽  
Kidney Microsomes ◽  
Alpha 7 ◽  
Cytochrome P 450

The cytochrome P-450 enzyme which catalyses 25-hydroxylation of vitamin D3 (cytochrome P-450(25] from pig kidney microsomes [Postlind & Wikvall (1988) Biochem. J. 253, 549-552] has been further purified. The specific content of cytochrome P-450 was 15.0 nmol.mg of protein-1, and the protein showed a single spot with an apparent isoelectric point of 7.4 and an Mr of 50,500 upon two-dimensional isoelectric-focusing/SDS/PAGE. The 25-hydroxylase activity towards vitamin D3 was 124 pmol.min-1.nmol of cytochrome P-450-1 and towards 1 alpha-hydroxyvitamin D3 it was 1375 pmol.min-1.nmol-1. The preparation also catalysed the 25-hydroxylation of 5 beta-cholestane-3 alpha,7 alpha-diol at a rate of 1000 pmol.min-1.nmol of cytochrome P-450-1 and omega-1 hydroxylation of lauric acid at a rate of 200 pmol.min-1.nmol of cytochrome P-450-1. A monoclonal antibody raised against the 25-hydroxylating cytochrome P-450, designated mAb 25E5, was prepared. After coupling to Sepharose, the antibody was able to bind to cytochrome P-450(25) from kidney as well as from pig liver microsomes, and to immunoprecipitate the activity for 25-hydroxylation of vitamin D3 and 5 beta-cholestane-3 alpha,7 alpha-diol when assayed in a reconstituted system. The hydroxylase activity towards lauric acid was not inhibited by the antibody. By SDS/PAGE and immunoblotting with mAb 25E5, cytochrome P-450(25) was detected in both pig kidney and pig liver microsomes. These results indicate a similar or the same species of cytochrome P-450 in pig kidney and liver microsomes catalysing 25-hydroxylation of vitamin D3 and C27 steroids. The N-terminal amino acid sequence of the purified cytochrome P-450(25) from pig kidney microsomes differed from those of hitherto isolated mammalian cytochromes P-450.

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