Reaction of the microsomal heme oxygenase with cobaltic protoporphyrin IX, and extremely poor substrate.
A reconstituted heme oxygenase system which was composed of a purified heme oxygenase from pig spleen microsomes and a partially purified NADPH-cytochrome c reductase from pig liver microsomes could not catalyze the conversion of cobaltic protoporphyrin IX (Co-heme) to biliverdin, although Co-heme could bind with the heme oxygenase protein to form a complex. The heme oxygenase system in the microsomes from pig spleen, rat spleen, and rat kidney also failed to oxidize Co-heme to biliverdin. Properties of the complex of Co-heme and heme oxygenase closely resembled those of cobalt myoglobin and cobalt hemoglobin; the Co-heme bound to the heme oxygenase protein did not react with cyanide and azide, the Co-heme moiety was reduced but only slowly with sodium dithionite, and the reduced form of the Co-heme did not appear to bind carbon monoxide. The co-heme bound to heme oxygenase was not reduced with the NADPH-cytochrome c reductase system in air. These findings further support the views that heme oxygenase may have a heme- binding crevice similar to those of myoglobin and hemoglobin and that reduction of heme is the prerequisite for the oxidative degradation of heme in the heme oxygenase reaction.[1]References
- Reaction of the microsomal heme oxygenase with cobaltic protoporphyrin IX, and extremely poor substrate. Yoshida, T., Kikuchi, G. J. Biol. Chem. (1978) [Pubmed]
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