Studies on reconstituted myoglobins and hemoglobins. I. role of the heme side chains in the oxygenation of myoglobin

Kuniyasu Kawabe*, Kazuhiko Imaizumi, Kiyohiro Imai, Itiro Tyuma, Hisanobu Ogoshi, Takahisa Iwahara, Zen Ichi Yoshida

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


To clarify the functional role of the 2- and 4-side chains of heme in myoglobin oxygenation, we synthesized several new hemins carrying nonnatural side chains at positions 2 and 4, reconstituted myoglobins with them, and investigated their optical, ionization, and oxygen-binding properties. The absorption maxima for most of the reconstituted myoglobins except those reconstituted with hemins having carbonyl groups, no matter whether they are oxy-, deoxy-, or carbon monoxy-form, shifted by at most 20 nm toward shorter wavelengths than protoheme-myoglobin. The absorption spectrum is more affected by resonance effects than by inductive effects of the peripheral side chains of heme. Differences in optical and oxygenation properties between isomeric myoglobins carrying hemes with different side chains at positions 2 and 4 indicate that the 2- and 4-side chains of heme are functionally nonequivalent, as previously shown by Sono and Asakura [(1975) J. Biol. Chem. 250, 5227-5232] for monoformyl-monovinylheme myoglobins. Modification of the 4-side chain exerts greater influence on the oxygen affinity than that of the 2-side chain. The extrapolation method proposed by Sono and Asakura to correct for the protein factor seems to be applicable only as a special case and does not apply to the isomeric myoglobins studied by us. There was not correlation between pK2

Original languageEnglish
Pages (from-to)1703-1712
Number of pages10
JournalJournal of Biochemistry
Issue number6
Publication statusPublished - 1982 Oct
Externally publishedYes

ASJC Scopus subject areas

  • Statistics, Probability and Uncertainty
  • Applied Mathematics
  • Physiology (medical)
  • Radiology Nuclear Medicine and imaging
  • Molecular Biology
  • Biochemistry


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