Measurement of cytochrome P-450

The family of cytochrome P-450 enzymes are involved in the metabolism of xenobiotics. This unit provides protocols for the three most common ways to measure cytochrome P-450. Spectrophotometric detection of the Soret band gives a quantitative measure of total cytochrome P-450 in microsomes, liver homogenate, or mitochondria, but lacks information about the specific P-450 forms. Immunochemical methods such as immunoblotting provide very sensitive semiquantitative identification of specific P-450 enzymes Finally, enzymatic assays depend on substrate specificity and also provide information about specific P-450 enzymes, although some members of this group of enzymes have broad and sometimes overlapping specificities.