Cytochrome P450 enzymes help metabolize most drugs and environmental toxins. They are found in the liver and in our small intestine, for example. We have many slightly different versions of cytochrome P450 (“CYP”), we call them “isoforms”. I work with the CYP isoforms most important in drug metabolism, in particular CYP3A4. We can use genetically modified E. coli bacteria to make the CYP, then study e.g. its drug binding by UV-Vis spectroscopy and drug metabolism by enzymatic assays. Through site-directed mutagenesis we can modify key amino acids and learn about their effects on the resulting mutant CYPs. This serves to better understand CYP enzymes at a fundamental, biochemical level.