ðɪ ˈɛnzaɪm sˌiːwˌaɪpˈiː θɹˈiː ˈeɪ fˈoːɹ, ɐ mˈɛmbɚɹ ʌvðə sˈaɪɾəkɹˌoʊm pˈiː fˈoːɹhˈʌndɹɪd fˈɪfti ˈɛnzaɪm fˈæmɪli, ɪz pɹˈɛzənt mˈoʊstli ɪnðə lˈɪvɚ bˌʌt ˈɔːlsoʊ ɪnðə lˈaɪnɪŋ ʌvðə ɡˌæstɹoʊɪntˈɛstɪnəl dʒˌiːˈaɪ tɹˈækt.
The enzyme CYP3A4, a member of the Cytochrome P450 enzyme family, is present mostly in the liver but also in the lining of the gastrointestinal (GI) tract.