Mytilus galloprovincialis CYP1A-like mRNAs reveal closer proximity of mytilid CYP1A to the eumetazoan CYP2 family

Due to the role of Cytochrome P450, Family 1, Subfamily A (CYP1A) in the detoxification of many polycyclic aromatic hydrocarbons (PAHs), there has been an effort to characterise the gene and the products from its expression in organisms that are relevant for biomonitoring and toxicity testing procedures. Nonetheless, the existence of functional homologues in aquatic invertebrates is not entirely consensual, especially in bivalve molluscs, which pose as one of the most important models for aquatic toxicologists, especially mytilids. After isolation and sequencing of CYP1A-like mRNA from the Mediterranean mussel, Mytilus galloprovincialis, phylogenetics incorporating homologues from molluscs and other eumetazoans, vertebrates included, yielded notorious similarity to sequences belonging to the CYP2 Family. Altogether, the findings further indicate that CYP1A-like CYPs may be absent in bivalves, in lieu of Families CYP2, 3 and 4, suggesting caution when interpreting data from common biomarkers of exposure to aromatic hydrocarbons that have been developed for CYP1A activity and expression in higher deuterostomes.