β-Naphthoflavone induced CYP1A1 and 1A3 proteins in the liver of rainbow trout (Oncorhynchus mykiss)

Abstract

1. Two CYP1A proteins, designated HAP 1 andHAP 2, were isolated from the liver of the β-naphthoflavone(BNF)-treated rainbow trout. The proteins were initially resolved by chromatography on a DEAE sepharose column and were further purified by hydroxylapatite chromatography. 2. Both HAP 1 and HAP 2 proteins exhibited high 7-ethoxyresorufin, methoxy resorufin and phenacetin O-dealkylase activities and were good catalysts for the oxidation of 7,12-dimethylbenz[a]anthracene (DMBA). No qualitative difference was observed between the two proteins in their ability to catalyse the formation of the individual metabolites of DMBA. 3. The two purified proteins showed identical amino acid sequence for the first 13 amino acids. However, the 14th amino acid was valine for HAP 1 protein and alanine for HAP 2 protein. 4. Alignment ofthe amino acid sequences showed that HAP 1 protein was identical to the deduced protein ofthe previously reported troutCYP1A2 (renamed CYP1A1) gene for the first 24 amino acids at the N-terminal region. HAP 2 protein corresponded to the deduced protein sequence of CYP1A3 gene for the first 14 amino acids. However, unlike the deduced sequences of CYP1A1 and 1A3 the N -terminal methionine was absent in the purified proteins. 5. We conclude thatHAP 1 and HAP 2 are the products ofthe CYP1A1 and CYP1A3 genes respectively, and are found in the liver of the BNF-treated rainbow trout.