Induction of nuclear styrene monooxygenase and epoxide hydrolase in rat liver

The apparent Km and Vmax of styrene monooxygenase and styrene epoxide hydrolase were determined in intact nuclear preparations from male rat liver after in vivo treatment with phenobarbital and beta-naphthoflavone, which are known to induce microsomal cytochrome P-450 and cytochrome P-448 respectively. Treatment with phenobarbital does not alter the apparent Km, but greatly increases the Vmax of both nuclear styrene monooxygenase and styrene epoxide hydrolase. Almost the same pattern is observed for styrene monooxygenase after treatment with beta-naphthoflavone, whereas the same treatment slightly increases both the Vmax and Km value of styrene epoxide hydrolase.