[Hepatic and duodenal biotransformation in Japanese quail (Coturnix coturnix): activities of 7-ethoxycoumarin O-deethylase and coumarin 7-hydroxylase].

In vitro cytochrome P-450-dependent monooxygenase activity was studied in hepatic and duodenal microsomes from the Japanese quail (Coturnix coturnix) with two substrates, 7-ethoxycoumarin and coumarin. The rate of formation of 7-hydroxycoumarin--as the main metabolic product--was followed by fluorometry. 7-Ethoxycoumarin O-de-ethylase activity (7-ECOD) was shown in liver and duodenum, but coumarin 7-hydroxylase (Cou 7-OH) was found only in liver. The requirement for some cofactors (NADPH), the inhibitory action of CO, optimal pH and temperature, kinetic constants (Km, Vm, and the spectral dissociation constant, Ks) were determined in all cases. Specific activities were found in the range 1-4 nmole/mg/min, 0.1-1 nmole/mg/min, and 0.5-3 nmole/mg/min for hepatic and duodenal 7-ECOD and hepatic Cou 7-OH, respectively. The coumarin 7-hydroxylase activity showed some striking features, inhibition by excess of substrate and high inhibition by alcohols.