Reaction of hemoglobin with HOCl: Mechanism of heme destruction and free iron release

Dhiman Maitra, Jaeman Byun, Peter R. Andreana, Ibrahim Abdulhamid, Michael P. Diamond, Ghassan M. Saed, Subramaniam Pennathur, Husam M. Abu-Soud

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Hypochlorous acid (HOCl) is generated by myeloperoxidase using chloride and hydrogen peroxide as substrates. HOCl and its conjugate base (OCl-) bind to the heme moiety of hemoglobin (Hb) and generate a transient ferric species whose formation and decay kinetics indicate it can participate in protein aggregation and heme destruction along with subsequent free iron release. The oxidation of the Hb heme moiety by OCl- was accompanied by marked heme destruction as judged by the decrease in and subsequent flattening of the Soret absorbance peak at 405 nm. HOCl-mediated Hb heme depletion was confirmed by HPLC analysis and in-gel heme staining. Exposure of Hb to increasing concentrations of HOCl produced a number of porphyrin degradation products resulting from oxidative cleavage of one or more of the carbon-methene bridges of the tetrapyrrole ring, as identified by their characteristic HPLC fluorescence and LC-MS. A nonreducing denaturing SDS-PAGE showed several degrees of protein aggregation. Similarly, porphyrin degradation products were identified after exposure of red blood cells to increasing concentrations of HOCl, indicating biological relevance of this finding. This work provides a direct link between Hb heme destruction and subsequent free iron accumulation, as occurs under inflammatory conditions where HOCl is formed in substantial amounts.

Original languageEnglish (US)
Pages (from-to)374-386
Number of pages13
JournalFree Radical Biology and Medicine
Issue number2
StatePublished - Jul 15 2011
Externally publishedYes


  • Free iron
  • Free radicals
  • Hemoglobin
  • Hypochlorous acid
  • Inflammation
  • Mammalian peroxidase
  • Oxidative stress
  • RBC

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


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