Adrenodoxin is a small iron-sulfur protein that can accept and carry a single electron. Adrenodoxin functions as an electron transfer protein in the mitochondrial cytochrome P450 systems.[7] The first enzyme in this system is adrenodoxin reductase that carries an FAD. FAD can be reduced by two electrons donated from coenzyme NADPH.[8] These two electrons are transferred one a time to adrenodoxin. Adrenodoxin in return reduces mitochondrial cytochrome P450.[7] This particular oxidation/reduction system is involved in the synthesis of steroid hormones in steroidogenic tissues. In addition, similar systems also function in vitamin D and bile acid synthesis in the kidney and liver respectively. Adrenodoxin has been identified in a number of different tissues but all forms have been shown to be identical and are not tissue specific.[6]
