sˈʌtʃ ˈɛnzaɪmz pɹˈɛzənt ɪnðə dʒˌiːˈaɪ tɹˈækt ɑːɹ ɐ fˈɜːst lˈaɪn dᵻfˈɛns ɐɡˈɛnst tˈɑːksɪk sˈʌbstənsᵻz; ðɪs ɐlˈaʊz ðə bˈɑːdi tə mətˈæbəlˌaɪz ɐwˈeɪ mˈɛni kˈɛmɪkəlz bᵻfˌoːɹ ðeɪ ˈɛntɚ ðə blˈʌdstɹiːm.
Such enzymes present in the GI tract are a first line defense against toxic substances; this allows the body to metabolize away many chemicals before they enter the bloodstream.