Moonlighting cytochrome P450 monooxygenases.

Recently, cytochrome P450 170A1 (CYP170A1) has been found to be a bifunctional protein, which catalyzes both monooxygenase activity and terpene synthase activity by two distinct active sites in the well-established P450 protein structure. Therefore, CYP170A1 is identified clearly as a moonlighting protein. The known activities of a small number of the 13,000 members of the P450 superfamily fall into two general classes: promiscuous enzymes that are not considered as moonlighting and forms that participate in biosynthesis of endogenous compounds, such as steroids, vitamins and play different roles in different tissues, sometimes being moonlighting enzymes. Here, we review examples of moonlighting P450, which add to our understanding of the large CYP superfamily.