CYP2A is a subfamily of CYPs, which includes but does not limit to CYP2A6 in human and CYP2A5 in mice (ref. 7). Coumarin is 7-hydroxylated specifically by coumarin 7-hydroxylase encoded by the mouse cyp2a5 gene and human cyp2a6 gene (ref. 7). Thus, activity of coumarin 7-hydroxylase is accepted as a marker of CYP2A5/6 catalytic activity. In the rest of this article, CYP2A5 and CYP2A6 are generally referred to CYP2A, and in catalytic enzyme level, they are referred to coumarin 7-hydroxylase.
