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Comparison of rates of enzymatic oxidation of aflatoxin B1, aflatoxin G1, and sterigmatocystin and activities of the epoxides in forming guanyl-N7 adducts and inducing different genetic responses.

Abstract：

:The genotoxicity of the dihydrofurans aflatoxin B1 (AFB1), aflatoxin G1 (AFG1), and sterigmatocystin (STG) was examined in a bacterial system in which the induction of SOS repair is monitored with the umuC gene linked to a lacZ reporter gene in plasmid pSK1002. Human liver microsomal cytochrome P-450NF oxidized the dihydrofurans (in the presence of calf thymus DNA) to give guanyl-N7 adducts in the order AFB1 greater than STG greater than AFG1. The order of the umu response seen was STG greater than AFB1 greater than AFG1, when either the dihydrofurans were activated enzymatically or the synthetic epoxides of the dihydrofurans were added directly to the bacteria. Thus, the umu response per molecule of guanyl-N7 DNA adduct follows the order STG greater than AFB1 greater than AFG1. A similar pattern has been reported in the literature for Salmonella typhimurium base substitution dependent his reversions, but the pattern AFB1 greater than STG greater than AFG1 has been found for bacterial frame-shift-dependent mutagenesis and hepatocarcinogenesis. The guanyl-N7 adduct derived from AFG1 has considerably less of all of these biological activities per molecule. Neither guanine imidazole ring opening nor apurinic site formation appears to be a factor involved in the differential biological responses seen with the three guanyl-N7 adducts. These findings indicate that these structurally related guanyl-N7 DNA adducts have intrinsic differences which give rise to divergent biological responses.

journal_name

Chem Res Toxicol

journal_title

Chemical research in toxicology

authors

Baertschi SW,Raney KD,Shimada T,Harris TM,Guengerich FP

doi

10.1021/tx00008a008

subject

Has Abstract

pub_date

1989-03-01 00:00:00

pages

114-2

issue

2

eissn

0893-228X

issn

1520-5010

journal_volume

2

pub_type

杂志文章

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