The effect of pH on the kinetics of bufuralol hydroxylation

Abstract

The 1'-hydroxylation of bufuralol in rat liver microsomes is catalysed by the same cytochrome P450 isoenzyme that catalyses the 4-hydroxylation of debrisoquine. A previous study has demonstrated that the kinetics of bufuralol hydroxylation in rat liver microsomes was non-hyperbolic although the same reaction occurring in human liver microsomes was consistent with simple Michaelis Menten kinetics. The effects of altering the pH of the incubation media on the kinetics of bufuralol hydroxylation was characterised in microsomes prepared from male Sprague-Dawley rats. Decreasing the pH (7.4 to 5.0) of the incubation medium produced a decrease in the reaction velocity that was associated with a trend towards hyperbolic kinetics. In contrast an increase in the pH (7.4 to 8.8) of the incubation media reduced the reaction velocity with only a minimal change in the kinetic profile of the reaction.