Characterization of a CYP3A-like activity in the digestive gland of Mytilus galloprovincialis-inhibition by 17alfa ethynylestradiol

CYP3A enzyme is a toxicologically relevant end-point; interactions between xenobiotics (e.g. pharmaceuticals and xenoestrogens) and CYP3A may compromise both the clearance of xenobiotics and endogenous molecules (e.g. steroid hormones), as they share common routes of metabolism through CYP3A enzymes. The purpose of this work was to better characterize CYP3A-like enzyme in microsomal fractions isolated from the digestive gland of mussels Mytilus galloprovincialis by using 7benzyloxy-4-trifluoromethylcoumarin as a substrate. The higher Km value in mussels collected from Barcelona harbor with respect to that collected from Ebro delta indicated lower affinity of the enzyme in polluted specimens. 17 alfa-ethynylestradiol (EE2)acted as mixed inhibitor of CYP3A activity. The study contributes to the better knowledge of CYP3A-like activity in mussels and shows potential interference between EE2 and possibly other pollutants, and CYP3A function.