Multiple forms of cytochrome P450 and associated monooxygenase activities in human brain mitochondria

We have investigated cytochrome P450 (P450) and associated monooxygenase ac tivities in human brain mitochondria isolated from eight regions of four hu man brain samples obtained at autopsy. P450-associated monooxygenase activi ties including aminopyrine N-demethylase (APD), 7-ethoxycoumarin O-deethyla se (ECD), p-nitrophenol hydroxylase (PNPH), and N-nitrosodimethylamine N-de methylase (ND-MAD) were detectable in the mitochondria from human brain reg ions. Immunoblot experiments using antisera to purified rat liver microsoma l P450, namely P4502B1/2, P4501A1/2,and P4502E1, revealed immunoreactive ba nds in isolated mitochondria from different regions of thr human brain. The antibody to P4502B1/2 and P4501A1/2 inhibited the human brain mitochondria l APD and ECD activities, respectively. The addition of antiserum to micros omal NADPH cytochrome P450 reductase did not affect the mitochondrial P450- associated monooxygenase activities, although it completely inhibited the c orresponding activities in brain microsomes. Overall, the present study dem onstrates, in human brain mitochondria, the presence of multiple forms of P 450 belonging to the 1A, 2B, and 2E subfamilies that are involved in xenobi otic metabolism (C) 2000 Elsevier Science Inc.