Cytochrome P450 protein, molecular model. This protein plays a crucial role in metabolism in animals (including humans), fungi, plants and bacteria. There are many different types of cytochrome P450 protein, but they all have a similar function; that of catalysing oxidation and reduction reactions. They are involved in manufacturing and breaking down hormones (such as testosterone), metabolising vitamin D and detoxifying substances (including drugs) in the liver. This last role makes understanding their activity extremely important in medicinal chemistry. In this model the secondary structure of the protein is seen, comprising alpha helices (red/green), beta sheets (cyan arrows) and linking regions (cyan lines).