Structure, function, regulation and polymorphism and the clinical significance of human cytochrome P450 1A2

Abstract

Human CYP1A2 is one of the major CYPs in human liver and metabolizes a number of clinical drugs (e.g., clozapine, tacrine, tizanidine, and theophylline; n > 110), a number of procarcinogens (e.g., benzo[a]pyrene and aromatic amines), and several important endogenous compounds (e.g., steroids). CYP1A2 is subject to reversible and/or irreversible inhibition by a number of drugs, natural substances, and other compounds. The CYP1A gene cluster has been mapped on to chromosome 15q24.1, with close link between CYP1A1 and 1A2 sharing a common 5′-flanking region. The human CYP1A2 gene spans almost 7.8 kb comprising seven exons and six introns and codes a 515-residue protein with a molecular mass of 58,294 Da. The recently resolved CYP1A2 structure has a relatively compact, planar active site cavity that is highly adapted for the size and shape of its substrates. The architecture of the active site of 1A2 is characterized by multiple residues on helices F and I that constitutes two parallel substrate binding platforms on either side of the cavity. A large interindividual variability in the expression and activity of CYP1A2 has been observed, which is largely caused by genetic, epigenetic and environmental factors (e.g., smoking). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. Induction or inhibition of CYP1A2 may provide partial explanation for some clinical drug interactions. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of them have been associated with altered drug clearance and response and disease susceptibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.

Keywords::

• CYP1A2
• substrate
• structure
• inhibitor
• regulation
• single nucleotide polymorphism

Acknowledgements

The authors appreciate the grant support of RMIT Health Innovations Research Institute, RMIT University, Bundoora, Victoria 3083, Australia and National Institute of Complementary Medicine, New South Wales, Australia. Dr. Li-Ping Yang was a holder of the Australian Postgraduate (Ph.D.) Awards (APA) funded by the Commonwealth Government of Australia. We also appreciate the support of Professor Hualiang Jiang, Ph.D. (Center for Drug Discovery and Design, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China).

We also appreciate the grant support from the National Health and Medical Research Council of Australia, Australia Research Council, and Cancer Council of Victoria, Australia.

Declaration of interest: All authors have no conflict of interest.