PMID-sentid Pub_year Sent_text comp_official_name comp_offsetprotein_name organism prot_offset 2486279-3 1989 Porphyrinogenic drugs act by lowering a regulatory "free heme pool" by three different mechanisms: (a) by mechanism-based inactivation of cytochrome P-450 resulting in N-alkylprotoporphyrin formation and ferrochelatase inhibition, (b) by mechanism-based inactivation of cytochrome P-450 resulting in continuous heme destruction, (c) by enhanced generation of active oxygen species which interact with an endogenous substrate to form an inhibitor of uroporphyrinogen decarboxylase. Oxygen 366-372 ferrochelatase Gallus gallus 204-218