Molecular cloning of CYP4 and GSTpi homologues in the scallop Chlamys farreri and its expression in response to benzo[a]pyrene exposure.

Cytochrome P450 enzymes (CYP) and glutathione s-transferases (GST) are essential components of cellular detoxification systems. In this study we cloned full-length cDNAs encoding CYP4 and GSTpi homologues from scallop Chlamys farreri. Both sequences were deposited in the GenBank with accession no. ACL80141 for CYP4 and ACL80138 for GSTpi. The sequence called Cf (C. farreri) CYP4 is constituted by an ORF of 1317 bp encoding for a protein of 50.8 kDa. The CfGSTpi is constituted by an ORF of 618 bp encoding for a protein of 23.9 kDa. The comparison of the deduced amino acid sequences with CYP4 and GSTpi from vertebrates showed high conservation of the residues and domains essential to the function of these two enzymes. CfCYP4 and CfGSTpi mRNA expression was detected in digestive gland, gill, mantle, mature female gonad and adductor. We then utilized the real-time PCR to study expression levels of the CfCYP4 and CfGSTpi gene in response to exposure of Benzo[a]pyrene (BaP) (0.01 and 0.2 μg/L) for 10 days. The results showed that during the exposure to BaP, CfCYP4 was significantly decreased in the gill and digestive gland of scallops, and CfGSTpi was increased on day 3 until the end of exposure. The changes in CfGSTpi mRNA levels observed in scallops exposed to BaP indicated that GSTpi could play an important role in the detoxification of BaP.