Effects of pH and Temperature on Mixed-Function Oxidases in the Liver of Cultured Fish

Abstract

Effects of pH and temperature on two mixed-function oxidases, aniline-p-hydroxylase and aminopyrine-N-demethylase, in the liver of cultured carp Cyprinus carpio, eel Anguilla japonica, yellowtail Seriola quinqueradiata, and red sea bream Pagrus major were studied.
The pH optima for aniline-p-hydroxylase were 7.5, 7.8, 7.5, and 7.3, in carp, eel, yellowtail, and red sea bream, respectively; and those for aminopyrine-N-demethylase were 7.3 in carp and 7.5 in other fishes. After 30min incubation, aniline-p-hydroxylases of carp and yellowtail showed the highest activity at 33°C and those of other fishes at 27°C. After 15min incubation, aminopyrine-N-demethylase showed the highest activity at 35°C, 37°C, and 40°C in red sea bream, carp, and two other fishes, respectively.