Porphyrin Traps Its erminator!Concerted and Stepwise Porphyrin Degradation Mechanisms Induced by Heme-Oxygenase and Cytochrome P450

摘要

The enzyme heme-oxygenase (HO)traps hem species and induces their degradation.The degradation process (Scheme 1)is thought to serve three key functions:a)maintenance of iron homeostasis,b)creation of CO in the brain that acts as a neurotransmitter akin to NO,and c)generation of products (e.g.,biliverdin)that play a role in the defense mechanism against oxidatie stree.Structural studies by Poulos and co-workers of the human form (hHO-1)of the enzyme-heme complex show that the trapped heme undergoes ligation by an imidazole ring of a histidine side chain adn a water molecule.