A helping hand for cytochrome p450 enzymes

In this issue of Cell Metabolism, Espenshade and colleagues (Hughes et al., 2007) show that the hemoprotein Dap1/PGRMC1 forms a stable complex with several members of the cytochrome P450 superfamily of enzymes and positively regulates their activities. This action indicates an important role for Dap1/PGRMC1 in P450-catalyzed reactions, some of which are involved in the metabolism of sterols and pharmaceutical compounds.