Activation of MeIQ (2-amino-3,4-dimethylimidazo- [4,5-f]quinoline) by sequence variants of recombinant human cytochrome P450 1A2

Abstract

Understanding the relationships between the sequences and catalytic activities of P450 enzymes that catalyze the bioactivation of mutagens and carcinogens is an important goal in mutation research. Escherichia coli strain DJ4309 expresses recombinant human P450 1A2 and activates promutagens such as MeIQ (2‐amino‐3,4‐dimethylimidazo[4,5‐f]quinoline), as measured by induction of reverse mutations detected as lacZ+ colonies on minimal lactose (ML) plates. Pools of P450 1A2 mutants were constructed by polymerase chain reaction (PCR) mutagenesis of putative substrate recognition sites (SRSs). Cultures of individual clones were patched onto MeIQ/ML plates and the growth of revertant microcolonies within each patch was inspected after 2 days of incubation. Beginning with a pool of several thousand clones, we identified 25 distinct P450 1A2 SRS variants with altered activities. In this study, the MeIQ dose‐responses of all the variants are reported. The implications of the results are considered with reference to published models of the protein's structure. Environ. Mol. Mutagen. 35:328–335, 2000 © 2000 Wiley‐Liss, Inc.

Cytochrome P450 expression and regulation in the brain

“…CYP1A is a central enzyme during phase I drug metabolism and contributes to the biotransformation of nearly 9% of clinical drugs, such as caffeine, analgesics, antipyretics, antipsychotics, antidepressants, and anti-inflammatory drugs (Lu et al 2020). In addition to medicines, CYP1A is also involved in the biological activation or deactivation of a large number of pollutants in the environment, such as benzopyrene, aristolochic acid I, ellipticine, PhIP (2amino-1-methyl-6-phenylimidazo(4,5-b)pyridine), and IQ (2-amino-3-methylimidazo[4,5-f]quinolone) (Abdel-Razzak et al 1994;Josephy et al 2000;Stiborov a et al 2001;Cheung et al 2005;Kotrbov a et al 2011). Furthermore, CYP1A1 and CYP1A2 metabolize sex hormones (including progestogens, androgens, and estrogens), retinol, melatonin, linoleic acid, phosphatidylcholine, and uroporphyrinogen (Shou et al 1997;Niwa et al 1998;Sinclair et al 1998;Yamazaki et al 1998;Yun et al 1999;Chen et al 2000;Moran et al 2000;Ohe et al 2000;Schwarz et al 2000;Von Bahr et al 2000;Ma et al 2005;Phillips et al 2011).…”

Cytochrome P450 Activation of Arylamines and Heterocyclic Amines

“…S. typhimurium tester strains have also been used to express human P450s that activate arylamines and HAAs (73,79,80). The E. coli strains overexpressing P450s and NAT have been used to characterize P450 1A2 allelic and random variants (81)(82)(83)(84). Another use of this genotoxicity system has been the screening and characterization of P450 inhibitors.…”

Five novel natural allelic variants?951A>C, 1042G>A (D348N), 1156A>T (I386F), 1217G>A (C406Y) and 1291C>T (C431Y)?of the human CYP1A2 gene in a French Caucasian population

“…However, the I386F substitution, which lies within a putative substrate recognition site, is likely to have an impact on CYP1A2 enzymatic activity, as suggested by previous sitechected mutagenesis experiments (Josephy et al, 2000).…”