A cytochrome P4501B gene from a fish, Pleuronectes platessa

Area of Science:

• Environmental Toxicology
• Molecular Biology
• Marine Biology

Background:

• Tetrapod cytochrome P4501 (CYP1) enzymes metabolize environmental contaminants like polycyclic aromatic hydrocarbons (PAHs).
• Mammalian CYP1A1/CYP1A2 diverged post-mammalian evolution, while fish possess a single CYP1A gene with mixed mammalian isoform properties.
• The evolutionary and toxicological roles of CYP1B genes in fish remain less understood.

Purpose of the Study:

• To isolate and characterize a novel CYP1 family gene from marine flatfish (plaice).
• To investigate the evolutionary relationship and functional properties of this piscine CYP1B gene.
• To determine its tissue expression and response to environmental inducers.

Main Methods:

• Gene isolation and sequencing from plaice (Pleuronectes platessa).
• Sequence similarity and phylogenetic analysis compared to mammalian CYP1 enzymes.
• Molecular modeling of the enzyme's active site.
• Northern blotting for tissue expression analysis.
• Treatment with beta-naphthoflavone (BNF) to assess induction.

Main Results:

• A new piscine CYP1B gene was identified, showing 54% amino acid identity to mammalian CYP1B1.
• Molecular modeling indicated conserved substrate-contacting residues in the active site.
• Phylogenetic analysis suggests a common ancestry between plaice CYP1B and mammalian CYP1B1.
• Plaice CYP1B was primarily detected in gill tissue, unlike the more widespread plaice CYP1A.
• Plaice CYP1B expression was not induced by the PAH-type inducer BNF.

Conclusions:

• Plaice CYP1B represents a distinct evolutionary lineage within the CYP1 family, related to mammalian CYP1B1.
• Its restricted tissue distribution and lack of induction suggest a specialized role in fish toxicology.
• This finding contributes to understanding the diversity and evolution of xenobiotic metabolism in vertebrates.