The involvement of CYP1A2 in biodegradation of dioxins in pigs

PLoS One. 2022 May 26;17(5):e0267162. doi: 10.1371/journal.pone.0267162. eCollection 2022.

Abstract

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is one of the most harmful chemicals showing resistance to biodegradation. The majority of TCDD effects is mediated by the aryl hydrocarbon receptor (AhR) pathway. TCDD binding to AhR results in the activation of cytochrome P450 enzymes (CYP1A1, CYP1A2, CYP1B1) involved in dioxin biodegradation. The goal of the study was to explore the potential role of CYP1A2 in the metabolism of TCDD. We investigated a molecular structure of CYP1A2 and the binding selectivity and affinity between the pig CYP1A2 and: 1/ DiCDD or TCDD (dioxins differing in toxicity and biodegradability) or 2/ their selected metabolites. pCYP1A2 demonstrated higher affinity towards DiCDD and TCDD than other pCYP1 enzymes. All dioxin-pCYP1A2 complexes were found to be stabilized by hydrophobic interactions. The calculated distances between the heme oxygen and the dioxin carbon nearest to the oxygen, reflecting the hydroxylating potential of CYP1A2, were higher than in other pCYP1 enzymes. The distances between the heme iron and the nearest dioxin carbon exceeded 5 Å, a distance sufficient to allow the metabolites to leave the active site. However, the molecular dynamics simulations revealed that two access channels of CYP1A2 were closed upon binding the majority of the examined dioxins. Moreover, the binding of dioxin metabolites did not promote opening of channel S-an exit for hydroxylated products. It appears that the undesired changes in the behavior of access channels prevail over the hydroxylating potential of CYP1A2 towards TCDD and the favorable distances, ultimately trapping the metabolites at the enzyme's active site.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carbon
  • Cytochrome P-450 CYP1A1 / metabolism
  • Cytochrome P-450 CYP1A2 / metabolism
  • Dioxins* / metabolism
  • Heme
  • Oxygen
  • Polychlorinated Dibenzodioxins*
  • Receptors, Aryl Hydrocarbon / metabolism
  • Swine

Substances

  • Dioxins
  • Polychlorinated Dibenzodioxins
  • Receptors, Aryl Hydrocarbon
  • Heme
  • Carbon
  • Cytochrome P-450 CYP1A1
  • Cytochrome P-450 CYP1A2
  • Oxygen

Grants and funding

This study was supported by National Science Centre, Poland (2016/21/N/NZ9/02320, 2012/05/B/NZ9/03333) and The Ministry of Science and Higher Education in Poland (UWM No. 528.0206.0806). This research was supported in part by PLGrid Infrastructure. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.