CHARACTERIZATION OF CYTOCHROME-P450 DEPENDENT MIXED-FUNCTION OXIDASE SYSTEM OF GILTHEAD SEABREAM (SPARUS-AURATA, SPARIDAE) LIVER

1. The average cytochrome P450 content of gilthead seabream liver microsomes was found to be 0.078 +/- 0.012 (n = 4) nmol/mg protein, which was about 50%, 24% and 13% of that measured in trout, sturgeon and scup fiver microsomes, respectively. 2. Gilthead seabream liver microsomes contained a relatively higher amount of cytochrome b5, as 0.32 +/- 0.05 (n = 4) nmol/mg protein. 3. Effects of microsomal protein amount and temperature ranging from 15 to 30-degrees-C on aniline 4-hydroxylation and ethylmorphine N-demethylation activities were examined. No significant differences were observed between the enzyme activities at these temperatures. 4. The liver microsomal aniline 4-hydroxylase activity of gilthead seabream in the 1990 fall (0.016-0.021 nmol p-aminophenol/min/mg protein) was 4.56 times higher than that in the 1991 spring (0.003-0.004 nmol p-aminophenol/min/mg protein). 5. Liver microsomal ethylmorphine N-demethylase activity measured in 1991 spring (0.371 nmol formaldehyde/min/mig protein) was 41% higher than that in 1990 fall (0.263 nmol formaldehyde/min/mg protein).