Cytochrome P450 isozymes catalyzing the hepatic microsomal oxidation of 9-anthraldehyde to 9-anthracene carboxylic acid in adult male rats.
Microsomal aldehyde oxygenase (MALDO) activity for 9-anthraldehyde (9-AA) was significantly higher in the male than in the female adult rat liver. 9-AA MALDO activity was also significantly enhanced by pretreatment with dexamethasone and phenobarbital, whereas it was not significantly changed by 3-methylcholanthrene or acetone. Several cytochrome P450 isozymes purified from rat hepatic microsomes were able to catalyze the oxidation of 9-AA to 9-anthracene carboxylic acid (9-ACA) in the presence of NADPH, NADPH-cytochrome P450 reductase and dilauroylphosphatidylcholine. Under the ordinary conditions of the reconstituted system, the catalytic activities (nmol/min/nmol P450) of cytochrome P450s, 2A1, 2B2, 2C6, 2C11 and 3A2 were 1.53 (1.37 in the presence of cytochrome b5), 1.20 (2.06), 4.87 (7.75), 18.0 (21.6) and 0.90 (1.17), respectively. Cytochrome P450 2C11 (CYP 2C11) showed the highest catalytic activity of the cytochromes examined. In the reconstituted system using the lipids extracted from microsomes, CYP 3A2 more effectively catalyzed the oxidation of 9-AA to 9-ACA, and its catalytic activity (nmol/min/nmol P450) was 3.33 or 6.61 in the absence or presence of cytochrome b5, respectively. The antibody against CYP 2C11 inhibited by 90% the hepatic microsomal oxidation of 9-AA MALDO activity in adult male rats, but the activity was not inhibited by antibody against CYP 3A2. These results show that the individual forms of cytochrome P450 have a catalytic activity for the oxidation of 9-AA to 9-ACA, and that CYP 2C11 is the major constitutive catalyst of 9-AA MALDO activity in untreated adult male rat liver.
Matsunaga
T
T
Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Kanazawa, Japan.
Iwawaki
Y
Y
Watanabe
K
K
Narimatsu
S
S
Yamamoto
I
I
Imaoka
S
S
Funae
Y
Y
Yoshimura
H
H
D000818:Animals; D000873:Anthracenes / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism
D000873:Anthracenes; D007527:Isoenzymes; C073050:9-anthraldehyde; C010030:9-anthroic acid; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase; C022657:steroid hormone 6-beta-hydroxylase