Measurement of Cytochrome P‐450

Abstract
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.