Prediction of regioselectivity and preferred order of metabolisms on CYP1A2-mediated reactions part 3: Difference in substrate specificity of human and rodent CYP1A2 and the refinement of predicting system.

Differences in CYP1A2-mediated metabolisms in human, rat and mouse have been analyzed with Template of human CYP1A2 established in our previous studies (Drug Metab Pharmacokinet 31:363, 2016 and 32:229, 2017). Using more than 25 chemicals including phenanthrene, MeIQx, PhIP, caffeine and furafylline, Template for human CYP1A2 was found to be applicable for rat and mouse CYP1A2 reactions with the consideration of five distinct regional interactions: 1) Expanded use of Ring D region of pro-metabolized molecules and also of trigger molecules, 2) acceptance of secondary amino groups at Position 31 of Ring eC1, 3) overlapping of pro-metabolized and trigger molecules at Ring eC4, 4) restricted maneuvering of substrates into Bay 1 region, and 5) allowance of passage of slightly large ligands in Thin-Area. These distinction points were found to be mutual for both substrates and inhibitors. In the present study, the decision-tree for substrates entering from Thin-Area has been reevaluated in consideration of species differences in human and rodent CYP1A2 forms. As the results, five steps of verification procedures have been introduced to predict the occurrence order of the regioselective metabolisms.