Effects of the arrangement of a distal catalytic residue on regioselectivity and reactivity in the coupled oxidation of sperm whale myoglobin mutants

Tatsuya Murakami, Isao Morishima, Toshitaka Matsui, Shin Ichi Ozaki, Isao Hara, Hui Jun Yang, Yoshihito Watanabe

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The coupled oxidations of sperm whale myoglobin (Mb) mutants are performed to examine active site residues controlling the regiospecific heme degradation. HPLC analysis of biliverdin isomers shows that L29H/H64L Mb almost exclusively gives biliverdin IXγ, although H64L and wild-type Mb mainly afford the α-isomer. Relocation of the distal histidine at the 43 and 107 positions increases the amount of γ-isomer to 44 and 22%, respectively. Interestingly, the increase in the ratio of γ-isomer is also observed by a single replacement of either His-64 with Asp or Phe-43 with Trp. It appears that the polarity of the active site as well as hydrogen bonding between oxygen molecule bound to the heme iron and His or Trp is important in controlling the regioselectivity. The results of coupled oxidation kinetics, autoxidation kinetics, and redox potential of the Fe3+/Fe2+ couple are discussed with regard to their implications for the active site and mechanism of heme oxygenase.

Original languageEnglish
Pages (from-to)2007-2011
Number of pages5
JournalJournal of the American Chemical Society
Volume121
Issue number10
DOIs
Publication statusPublished - 1999 Mar 17
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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