Cloning and Sequencing of Cytochrome P450 1A Complementary DNA in Eel (Anguilla japonica) Ryoichi Mitsuo, Takao Itakura,* and Mamoru Sato Faculty of Fisheries, Kagoshima University, 4-50-20, Shimoarata, Kagoshima 890-0056, Japan Abstract: Cytochrome P450 1A (CYP1A) complementary DNA was isolated from eel (Anguilla japonica) liver treated with 3-methylcholanthrene. The cDNA contained a 5' untranslated region of 163 bp, an open reading flame of 1560 bp coding for 519 amino acids and a stop codon, and a 3' untranslated region of 1730 bp. The predicted molecular weight was approximately 58.4 kDa. The deduced amino acid sequence exhibited identities with reported CYP1A sequences of 80% for rainbow trout, 79% for scup, 76% for plaice and butterfly fish, and 74% for toadfish. When compared with mammalian CYP proteins, the eel CYP1A was more similar to CYP1A1 (54%–56%) than to CYP1A2 (49%–52%). Northern and Southern blot analyses showed two distinct bands, suggesting the existence of another 3-methylcholanthrene-inducible CYP1A gene in eel. Key words: cytochrome P450 1A genes, eel, 3-methylcholanthrene, cDNA, Anguilla japonica I NTRODUCTION Cytochrome P450 (CYP) is a hemoprotein found in a mul- titude of animal and plant species (Nelson et al., 1996). The CYP enzymes, located mainly in the endoplasmic reticulum of various tissues, are engaged in the oxidative metabolism of a variety of substrates from endogenous compounds such as steroids, fatty acids, and prostaglandins, to numerous exogenous compounds including drugs, environmental car- cinogens, and natural products (Porter and Coon, 1991). The CYP genes have multiple molecular species and form a gene superfamily with 74 different gene families (Nelson et al., 1996). Some of the CYP gene families that can biotransform exogenous compounds (also referred to as xenobiotic chemicals) reveal great inducibility for those chemicals. In the xenobiotic metabolic gene families, a fam- ily designated CYP1 is known to be induced by polycyclic aromatic hydrocarbons and related compounds, such as 3-methylcholanthrene (3-MC), -naphthoflavone, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (Nebert and Gonzalez, 1987). CYP1 has two subfamilies, CYP1A and more recently discovered CYP1B (Sutter et al., 1994). Molecular characterization of CYP genes is important for understanding the mechanism of the induction of CYP enzymes in both toxicologic and environmental research. Molecular studies of teleost CYP1A has so far been reported for rainbow trout (Heilmann et al., 1988), plaice (Leaver et al., 1993), red sea bream (Mizukami et al., 1994), scup and toadfish (Morrison et al., 1995), butterfly fish (Vrolijk and Chen, 1995), and Atlantic tomcod (Roy et al., 1995). In this article, we present the results of CYP1A in eel (Anguilla japonica) and a phylogenetic analysis of CYP1A genes in fish. Received December 19, 1998; accepted February 18, 1999 *Corresponding author. fax +81-99-286-4015; e-mail itakura@zero.fish.kagoshima- u.ac.jp Mar. Biotechnol. 1, 353–358, 1999 © 1999 Springer-Verlag New York Inc.