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. Author manuscript; available in PMC: 2022 Feb 25.
Published in final edited form as: Crit Rev Biochem Mol Biol. 2021 Aug 25;56(6):640–668. doi: 10.1080/10409238.2021.1957668

Figure 4. Overview of the proposed reaction mechanism for the conversion of heme o to heme a.

Figure 4.

The C-8 methyl group (shown in red) loses a proton and two electrons, generating a carbocation. An oxygen atom from water (shown in red) traps this carbocation, yielding heme I, an alcohol intermediate. A second oxidation step ultimately converts the alcohol into an aldehyde, generating heme a.