Structures of Mitochondrial P450 System Proteins

Abstract

3 Mitochondrial P450 type enzymes are generally involved in the metabolism of cholesterol derived steroidal compounds. The reactions catalyzed by these enzymes include cholesterol conversion to pregnenolone, II-beta and 18 hydroxylation reactions in adrenal steroid biosynthesis, C-27 hydroxylation of cholic acid in bile acid metabolism, and lal-pha and 24 hydroxylations of vitamin D. These P450 mediated reactions require molecular oxygen and two electrons donated by NADPH. The electrons ofNADPH are transferred to P450 by an electron transfer system that includes a specific flavoprotein, adrenodoxin re-ductase, and an iron-sulfur protein, adrenodoxin. These proteins are not specific for individual P450s and serve as electron donors for different P450 in different tissues. This review presents an overview of the major sequence and structural characteristics of the mitochondrial P450 system proteins.