TY - JOUR
T1 - Heme oxygenase-2. Properties of the heme complex of the purified tryptic fragment of recombinant human heme oxygenase-2
AU - Ishikawa, K.
AU - Takeuchi, N.
AU - Takahashi, S.
AU - Matera, K. M.
AU - Sato, M.
AU - Shibahara, S.
AU - Rousseau, D. L.
AU - Ikeda-Saito, M.
AU - Yoshida, T.
PY - 1995
Y1 - 1995
N2 - Recombinant human microsomal heme oxygenase-2 was expressed in Escherichia coli. Tryptic digestion of the membrane fraction, in which the wild-type enzyme was localized, yielded a soluble tryptic peptide of 28 kDa, which retained the ability to accept electrons from NADPH-cytochrome P-450 reductase and the enzymatic activity for conversion of heme to biliverdin. The tryptic fragment, when purified to apparent homogeneity, bound one equivalent of home to form a substrate-enzyme complex that had spectroscopic properties characteristic of home proteins, such as myoglobin and hemoglobin. Optical absorption, Raman scattering, and EPR studies of the heme-tryptic fragment complex revealed that the ferric heme was six coordinate high spin at neutral pH and six coordinate low spin at alkaline pH, with a pK(a) value of 8.5. EPR and Raman scattering studies indicated that a neutral imidazole of a histidine residue served as the proximal ligand in the heme-heme oxygenase-2 fragment complex. The reaction with hydrogen peroxide converted the home of the heme oxygenase-2 fragment complex into a verdoheme-like intermediate, while the reaction with m-chloroperbenzoic acid yielded a oxoferryl species. These spectroscopic properties are similar to those obtained for home oxygenase-1, and thus the catalytic mechanism of heme oxygenase-2 appears to be similar to that of home oxygenase-1.
AB - Recombinant human microsomal heme oxygenase-2 was expressed in Escherichia coli. Tryptic digestion of the membrane fraction, in which the wild-type enzyme was localized, yielded a soluble tryptic peptide of 28 kDa, which retained the ability to accept electrons from NADPH-cytochrome P-450 reductase and the enzymatic activity for conversion of heme to biliverdin. The tryptic fragment, when purified to apparent homogeneity, bound one equivalent of home to form a substrate-enzyme complex that had spectroscopic properties characteristic of home proteins, such as myoglobin and hemoglobin. Optical absorption, Raman scattering, and EPR studies of the heme-tryptic fragment complex revealed that the ferric heme was six coordinate high spin at neutral pH and six coordinate low spin at alkaline pH, with a pK(a) value of 8.5. EPR and Raman scattering studies indicated that a neutral imidazole of a histidine residue served as the proximal ligand in the heme-heme oxygenase-2 fragment complex. The reaction with hydrogen peroxide converted the home of the heme oxygenase-2 fragment complex into a verdoheme-like intermediate, while the reaction with m-chloroperbenzoic acid yielded a oxoferryl species. These spectroscopic properties are similar to those obtained for home oxygenase-1, and thus the catalytic mechanism of heme oxygenase-2 appears to be similar to that of home oxygenase-1.
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U2 - 10.1074/jbc.270.11.6345
DO - 10.1074/jbc.270.11.6345
M3 - Article
C2 - 7890772
AN - SCOPUS:0028955429
SN - 0021-9258
VL - 270
SP - 6345
EP - 6350
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 11
ER -