Induction of the FAD synthetase system in rat liver by phenobarbital administration.

FMN and FAD synthesizing activities in rat liver were investigated when drug metabolizing enzymes were induced by phenobarbital. The FAD content of the liver mitochondrial and microsomal fractions were increased by either one shot administration or three successive daily administrations of phenobarbital. Similarly the flavokinase and FAD pyrophosphorylase activities also increased in the mitochondrial, microsomal and cytosol fractions. The authors have verified that activation of the FAD synthesizing system is induced by phenobarbital and suggest that the FMN and FAD contents are regulated not only by variations of flavin enzyme apoprotein, but also by changes in flavokinase and FAD pyrophosphorylase activities.