Activation of aflatoxin B1 by mouse CYP2A enzymes and cytotoxicity in recombinant yeast cells

Pelkonen, Paivi, Lang, Matti A., Wild, Christopher P., Negishi, Masahiko and Juvonen, Risto O. (1994) Activation of aflatoxin B1 by mouse CYP2A enzymes and cytotoxicity in recombinant yeast cells. European Journal of Pharmacology: Environmental Toxicology and Pharmacology, 292 1: 67-73.


Author Pelkonen, Paivi
Lang, Matti A.
Wild, Christopher P.
Negishi, Masahiko
Juvonen, Risto O.
Title Activation of aflatoxin B1 by mouse CYP2A enzymes and cytotoxicity in recombinant yeast cells
Formatted title Activation of aflatoxin B1 by mouse CYP2A enzymes and cytotoxicity in recombinant yeast cells
Journal name European Journal of Pharmacology: Environmental Toxicology and Pharmacology
Publication date 1994-11
Sub-type Article
DOI 10.1016/0926-6917(94)90027-2
Volume number 292
Issue number 1
ISSN 0926-6917
Start page 67
End page 73
Total pages 7
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Formatted abstract The ability of three highly homologous mouse liver CYP2A enzymes to activate aflatoxin B1 was studied by expressing them in recombinant AH22 Saccharomyces cerevisiae yeast cells. The reconstituted monooxygenase complex with CYP2A5 purified from yeast cell microsomes produced epoxide at a rate of 17.2 nmol/min per nmol P450 in the presence of 50 μM aflatoxin B1 while CYP2A4 had about 10% and P4507α only 1.5% of this activity. However, Km values were 530 and 10 μM and Vmax values 12.5 and 14.3 nmol/min per nmol P450 for CYP2A4 and CYP2A5, respectively. When recombinant yeast cells were exposed to aflatoxin B1 LC50 concentrations were 7.5 ± 5.5 μM for CYP2A4, 0.45 ± 0.10 μM for CYP2A5 and > 320 μM for P4507α expressing yeast cells. Aflatoxin B1-DNA adduct levels in the same yeast cells were 50, 890 pmol/mg DNA and below detection limit when 3.0 μM aflatoxin B1 was used in the incubation mixture. Coumarin an inhibitor for CYP2A4 and a substrate for CYP2A5 diminished the toxicity of aflatoxin B1 in a dose-dependent manner for these recombinant yeast cells. These data demonstrate that (1) highly homologous mouse CYP2A enzymes activate aflatoxin B1 in a different manner and (2) that recombinant yeast cells expressing mammalian CYP enzymes are a useful and inexpensive system to test the role of different enzymes in aflatoxin B1 toxicity. The data also indicate that mouse CYP2A5 and its counterpart in other species could have a significant role in aflatoxin B1 toxicity in organs where it is expressed at high levels.
Keyword Aflatoxin B1
Saccharomyces cerevisiae
CYP2A
Metabolic activation
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Title continues Environmental Toxicology and Pharmacology ISSN (1382-6689)

Document type: Journal Article
Sub-type: Article
Collection: National Research Centre for Environmental Toxicology Publications
 
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