Mixed function oxidase activity in a marsupial. The quokka (Seton;x brachyurus).

Components of the cytochrome P-450 pathway and rates of oxidative hepatic metabolism of the substrates, ethylmorphine, 3,4-benzpyrene, and aniline, have been investigated in a marsupial (the quokka, Setonix brachyurus) and compared with those of the rat. In general the quokka had lower rates of drug metabolism and higher KM values than those found in the rat. Sex differences in Vmax and KM were also found for the quokka. These species and sex differences in oxidative drug metabolism did not correlate with measured concentrations of cytochromes P-450 or b5 or with NADPH-cytochrome c reductase activities, and have been attributed to differences in both KM and Vmax values.