Functional characterization of a unique cytochrome P450 in Toxoplasma gondii

The basic metabolic cytochrome P450 (CYP) proteins are essential for the biotransformation of sterols and xenobiotics. By contrast, the Toxoplasma gondii genome contains only one CYP gene, and the role of this enzyme in the physiology and biochemistry of apicomplexan parasites is unknown. Because it is a potential resistance gene, identifying the functionality of P450 in T. gondii is particularly important. Knocking out Tg-P450 had no significant effect on T. gondii survival, but mice infected with parasites overexpressing Tg-P450 exhibited significantly enhanced pathogenicity. Enzyme activity analyses demonstrated that this protein has mammalian CYP2B and CYP3A enzymatic activity. In addition, T. gondii lacking the P450 gene exhibited reduced resistance to quinine, mefloquine and clarithromycin compared with parasites overexpressing Tg-P450. These results suggest that P450 functions in T. gondii metabolism and detoxification is involved in vitally important processes in parasitic organisms, making this enzyme a potential drug target.