1998 Fiscal Year Final Research Report Summary
Molucular mechanisms of oxygen activation at the three steps in heme oxygenase reaction
| Project/Area Number |
09480158
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional biochemistry
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| Research Institution | YAMAGATA UNIVERSITY |
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Principal Investigator |
YOSHIDA Tadashi YAMAGATA UNIVERSITY SCHOOL OF MEDICINE,DEPARTMENT OF BIOCHEMISTRY,PROFESSOR, 医学部, 教授 (10004673)
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| Co-Investigator(Kenkyū-buntansha) |
MIGITA Taiko YAMAGATA UNIVERSITY SCHOOL OF ALLIED HEALTH SCIENCES,ASSOCIATE PROFESSOR, 医療技術短期大学部, 助教授 (90159161)
FUJII Hiroshi INSTITUTE FOR MOLECULAR SCIENCE,ASSOCIATE PROFESSOR, 分子科学研究所, 助教授 (80228957)
ZHANG Zuhong YAMAGATA UNIVERSITY SCHOOL OF MEDICINE,DEPARTMENT OF BIOCHEMISTRY,INSTRUCTOR, 医学部, 助手 (10292442)
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| Project Period (FY) |
1997 – 1998
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| Keywords | ヘムオキシゲナーゼ / オキシゲナーゼ / 酵素活性化機構 / ヘム / ヘムの分解 / CO / ビリベルジン / ビリルビン |
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| Research Abstract |
(1)The resonance Raman spectra for alpha-hydroxyheme and verdoheme complexes of heme oxygenase (HO) was measured. We found that the ferric alpha-hydroxyheme and ferrous verdoheme complexes showed atypical Raman patterns, which are interpreted as the result of the symmetry lowering of the porphyrin-conjugating pi-electron system. (2)To identify the axial heme ligand of HO-2, we prepared His45 to Ala (H45A) and Hisi 52 to Ala (Hi 52A) mutants. H45A was completely devoid of the heme dedradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-H45A complex, On the contrary, H152A mutant exhibited spectroscopic and enzymatic properties identical to those of wild-type. His132 of HO-1 was also not important for the heme degradation. (3)The O_2 and CO reactions with the heme, hydroxyheme, and verdoheme complexes of HO were studied. The 02 affinities for heme and hydroxyheme are very high, but the CO affinities are only 1-6-fold higher than the O_2 affinities. Thus, HO discriminates much more strongly against CO binding than myoglobin. The CO affinities of the verdoheme complexes are about 10,000 times weaker than those of the heme complex. (4)On the basis of Raman spectra of O_2-bound form of the heme-HO complex, a highly bent Fe-O-O geometry has been proposed. However, the interaction of bound oxygen with the distal amino acid residue has not been identified. To clarify this, we have carried out EPR measurements of the cobalt(II) porphyrin HO complex and revealed that the bound-O_2 forms hydrogen-bond interactions with distal amino acid residue.
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