Bioactivation of Aromatic Amines by Human CYP2W1, An Orphan Cytochrome P450 Enzyme

The human genome contains approximately 13 orphan cytochrome P450 (P450, CYP) genes, of which the apparent function or substrate has not been identified. However, they seem to possess their own biological relevance in some tissues or developmental stages. Here, we characterized the heterologously expressed CYP2W1, an orphan P450 enzyme. The recombinant CYP2W1 protein containing a $6{\times}$(His)-tag at Nterminus has been expressed in Escherichia coli and purified. Expression level of CYP2W1 holoenzyme was around 500 nmol P450 holoenzyme per liter culture medium. The reduced CO difference spectrum of CYP2W1 showed a maximum absorption at 449 nm. CYP2W1 indicated the significant induction to bioactivate Trp-P-1, MeIQ, and IQ in E. coli DJ701 tester strain. However, the bioactivation of B[$\alpha$]P, and NNK by CYP2W1 was relatively low. The model structure of CYP2W1 suggested the characteristic P450 folds with the lengths and orientations of the individual secondary elements. The F-G loop is situated on the distal side of heme to accommodate the flexibility of active site of CYP2W1. These studies can provide useful information for the finding of its biological roles and structure-function relationships of an orphan CYP2W1 enzyme.