MONOOXYGENASE ACTIVITIES OF PARTIALLY PURIFIED CYTOCHROMES P-450 FROM HUMAN LIVER MICROSOMES

Publisher Summary This chapter discusses monooxygenase activities of partially purified cytochromes P-450 from human liver microsomes. Human liver microsomal cytochromes P-450 are of prominent pharmacotoxicological interest because they are key enzymes in drug metabolism. In this study, human livers were obtained from kidney transplantation donors. Liver was removed within one hour after circulatory arrest and immediately stored in solid CO 2 and then −80°C. Microsomes were prepared, solubilized in sodium cholate, and applied to a DEAE cellulose column; after elution, two peaks—A and B—of cytochrome P-450 were generally obtained. These fractions were concentrated by ultrafiltration, dialyzed buffer-exchanged on Sephadex G25, and applied to a CM cellulose column; after elution, four fractions were obtained: A gave A 1 and A 2 while B gave B 1 and B 2 . The results demonstrate good quality of starting material, which compares well with published results on cytochrome P-450 and monooxygenase activities of human liver and with those of control rat. For an unknown reason, 16-α-steroid hydroxylase activities were much lower than in control rats.