CHARACTERIZATION OF THE PRESENCE AND SEASONAL-VARIATION OF A CYP1A-LIKE ENZYME IN DIGESTIVE GLAND OF THE COMMON MUSSEL, MYTILUS-EDULIS

The presence and putative catalytic properties of a CYP1A-like enzyme in the digestive gland of Mytilus edulis L. were investigated by molec ular biological and seasonal studies. Reverse-transcriptase PCR using oligonucleotide primers to amplify a sequence around the conserved hae m binding cysteine region of hepatic CYP1A1 of trout (Oncorhynchus myk iss) produced several cDNA bands resolved by electrophoresis, includin g major bands of about 220 and 280 bp compared tb the predicted size f or O. mykiss of 208 bp. Following Southern blotting and probing with a cDNA probe to O. mykiss CYP1A1 (pfP(1)450-3' probe modified by remova l of 3'-non-coding region by digestion by Cla1), a single band (280 bp ) only was detected using moderate stringency conditions of sequence r ecognition (i.e. hybridization at 42 degrees C followed by washing at 55 degrees C in 1 x SSC containing 0.1% SDS), providing evidence for t he presence of a CYP1A orthologous gene sequence. The seasonal variati on in levels of putative CYP1A mRNA (Northern analysis using the modif ied cDNA probe for 0. mykiss CYP1A1) over 1 year showed some similarit y to seasonal patterns of change in microsomal metabolism of H-3-benzo [a]pyrene (BaP) to polar metabolites (diols, diones and phenols resolv ed by HPLC). Maxima for putative CYP1A mRNA and BaP metabolism levels were in late spring-early summer. However, differences were also appar ent, possibly indicative of other P450s contributing to BaP metabolism . Overall the results indicate the existence of a CYP1A-like enzyme wh ich is, at least, partly responsible for the mono-oxygenase activity o f BaP metabolism. Copyright (C) 1996 Elsevier Science Ltd