Compound I of heme oxygenase cannot hydroxylate its heme meso-carbon

Toshitaka Matsui*, Sun Hee Kim, Hiromichi Jin, Brian M. Hoffman, Masao Ikeda-Saito

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Heme oxygenase (HO) catalyzes heme catabolism through three successive oxygenation steps where the substrate heme itself activates O2. It has been thought that the reactive species responsible for the first heme oxygenation, meso-hydroxylation, is the hydroperoxy-ferric heme intermediate (Fe-OOH) rather than an oxo ferryl porphyrin cation radical, so-called compound I. A recent theoretical study (Kamachi, T.; Yoshizawa, K. J. Am. Chem. Soc. 2005, 127, 10686), however, proposed that compound I can oxidize its meso-carbon atom with the assistance of a bridging water molecule. In this communication, we report the first direct observation of compound I of a heme-HO-1 complex, generated by reaction of ferric-HO-1 with m-chloroperbenzoic acid. HO compound I slowly decays to compound II without producing any meso-hydroxylated products. It does react with guaiacol and thioanisole, however. Our findings unambiguously rule out involvement of compound I in the HO catalysis.

Original languageEnglish (US)
Pages (from-to)1090-1091
Number of pages2
JournalJournal of the American Chemical Society
Issue number4
StatePublished - Feb 1 2006

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry


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