Cytochromes P450 are a group of heme-thiolate monooxygenases. In liver microsomes, this enzyme is involved in an NADPH-dependent electron transport pathway. It oxidizes a variety of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics. an organic molecule + O2 + reduced [NADPH--hemoprotein reductase] = an alcohol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] P450 can be induced to high levels in liver and other tissues by various foreign compounds, including drugs, pesticides, and carcinogens. This protein differs from other forms of cytochrome P450 in that it catalyzes the 21-hydroxylation of progesterone, resulting in the formation of deoxycorticosterone. Belongs to the cytochrome P450 family.