7-Ethoxycoumarin dealkylase and cytochrome P-450 from grey partridge (Perdix perdix) hepatic and duodenal microsomes

Hepatic and duodenal microsomes were prepared from partridge by conventional procedures. The duodenal homogenates were stable, avoiding the use of protease inhibitors in the preparation of microsomes. Both microsomal fractions were able to dealkylate 7-ethoxycoumarin, showing the characteristics of a cytochrome P-450 dependent reaction. Parameters of the reaction (cofactor requirements, optimal pH, Km) were established. Typical type I difference spectrum was obtained upon addition of 7-ethoxycoumarin to hepatic and duodenal microsomes; with liver, Km and Ks values were similar. The concentration of cytochrome P-450 was very high and similar in both organs, but the specific activity of duodenal 7-ethoxycoumarin dealkylase was about 10% and NADPH-cytochrome c reductase 50% that of liver.