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Human serum albumin incorporating synthetic hemes as an O 2 ‐carrying hemoprotein: control of O 2 ‐binding ability by heme structure
Author(s) -
Tsuchida Eishun,
Komatsu Teruyuki,
Mastukawa Yasuko,
Okada Tomoyuki
Publication year - 2002
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200208)186:1<1::aid-masy1>3.0.co;2-m
Subject(s) - myoglobin , chemistry , heme , human serum albumin , hemeprotein , hemoglobin , histidine , adduct , stereochemistry , molecule , serum albumin , biochemistry , organic chemistry , amino acid , enzyme
Incorporation of different structured synthetic hemes, 5,10,15,20‐tetraphenylporphyrinatoiron(II) derivetives with a covalently linked proximal base [FeP( 1 ) to FeP( 7 )], into human serum albumin (HSA), provides seven types of albumin‐heme hybrids (HSA‐FeP) with different O 2 ‐binding abilities. An HSA host absorbs a maximum of eight FeP molecules in each case. The obtained all HSA‐FePs can reversibly bind and release O 2 under physiological conditions (in aqueous media, pH 7.3, 37°C) as similar as hemoglobin and myoglobin. The difference in the fence structures did not affect the O 2 ‐binding parameters, however the axial histidine coordination significantly increased the O 2 ‐binding affinity, which is ascribed to the low O 2 ‐dissociation rate constants. The most remarkable effect of the heme structure appeared in the half‐lifetime (τ 1/2 ) of the O 2 ‐adduct complex. The dioxygenated rHSA‐FeP( 4 ) showed an unusually long lifetime (τ 1/2 : 25 hr at 37°C) which is ca. 13‐fold longer than that of rHSA‐FeP( 1 ).