ABSTRACT
Adrenodoxin reductase was identified as a flavoprotein by T. Omura et al. Adrenodoxin reductase is flavin adenine dinucleotide-containing monomeric protein whose molecular weight is estimated to be approximately 54,000. The semiquinone form of adrenodoxin reductase is of the neutral type as judged by the visible absorption spectrum and electron paramagnetic resonance spectrum, but it is unique in that it binds NADPH. In the steroid hydroxylation system of adrenocortical mitochondria, adrenodoxin reductase and adrenodoxin are associated on the matrix side of the inner membrane, whereas cytochrome P-450s are located in the inner membrane of mitochondria. Adrenodoxin reductase consists of 492 amino acids including an extension peptide of 32 amino acid residues at the N-terminus. The reversibility of the electron flow from reduced adrenodoxin to NADP+ via adrenodoxin reductase was studied. The anaerobic photoreduction of adrenodoxin reductase in the presence of NADP+ and EDTA produced NADPH.
