Heme oxygenase mechanism

Ortiz De Montellano, P.R. (1998). Heme oxygenase mechanism Evidence for an electrophilic, ferric peroxide species. Accounts Chem. Res. 31, 543-549. 

Heme Oxygenase Structure and Mechanism Paul R. Ortiz de MonteBano and Angela Wilks... 

Fig. 1. Overview of intravascular heme catabolism. Hemoglobin, myoglobin, and other heme proteins are released into the circulation upon cellular destruction, and the heme moiety is oxidized by O2 to the ferric form (e.g., methemoglobin and metmyoglobin). Haptoglobin can bind a substantial amount of hemoglobin, but is readily depleted. Ferric heme dissociates from globin and can be bound by albumin or more avidly by hemopexin. Hemopexin removes heme from the circulation by a receptor-mediated transport mechanism, and once inside the ceU heme is transported to heme oxygenase for catabolism.

Although there is very little data on the mechanistic aspects of the biosynthetic enzymes, it is thought that their reaction mechanisms are very similar to those of the mammalian heme oxygenases. Indirect evidence that the mechanism of action of the biosynthetic enzymes is similar to that of the mammalian heme oxygenases was provided by 0-labeling studies showing that the biosynthesis of phycocyanobilin occurred via a two-molecule mechanism (141, 142) comparable to that of the mammalian heme oxygenases (8). 

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