Phenol-Sulfate Conjugating Activity in Liver-Soluble Fraction of Fish

The phenol-sulfate conjugation by the liver subcellular fractions from goldfish Carassius auratus, carp Cyprinus carpio, rainbow trout Salmo gairdneri, and Tilapia nilotica has been studied using [³⁵S] K₂SO₄. The cell fractionation of goldfish liver was examined by the determination of respective markers for nuclear, mitochondrial, lysosomal, microsomal, and soluble fractions. Among those subcellular fractions, only the soluble fraction displayed the conjugating activity. The maximum activity of the enzyme in the soluble fraction was obtained in the presence of 20 µmol of both ATP and Mg²⁺ in 1.5 ml of medium, although the activity decreased with an excess of ATP and Mg²⁺. This conjugation was inhibited by more than 0.1 µmol of Ca²⁺ in 1.5 ml of medium. The enzyme exhibited the conjugating activity in the pH range 7.5–9.5; the optimum value was at 8. In the temperature range 5–40°C, the maximum conjugation in goldfish, Tilapia, and carp occurred at 35°C, in rainbow trout it occurred at 30°C. The phenol-sulfate conjugating activities in goldfish, carp, rainbow trout, Tilapia and albino rat were approximately 340, 82, 66, 200 and 720 nmol/g-liver per h, respectively.