O2-mediated oxidation of ferrous nitrosylated human serum heme-albumin is limited by nitrogen monoxide dissociation |
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| Authors: | Ascenzi Paolo Gullotta Francesca Gioia Magda Coletta Massimo Fasano Mauro |
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| Affiliation: | aInterdepartmental Laboratory of Electron Microscopy, University Roma Tre, Via della Vasca Navale 79, I-00146 Roma, Italy;bNational Institute for Infectious Diseases I.R.C.C.S. ‘Lazzaro Spallanzani’, Via Portuense 292, I-00149 Roma, Italy;cDepartment of Experimental Medicine and Biochemical Sciences, University of Roma ‘Tor Vergata’, Via Montpellier 1, I-00133 Roma, Italy;dInteruniversity Consortium for the Research on the Chemistry of Metals in Biological Systems, Piazza Umberto I 1, I-87100 Bari, Italy;eDepartment of Structural and Functional Biology, and Center of Neuroscience, University of Insubria, Via Alberto da Giussano 12a, I-21052 Busto Arsizio, VA, Italy |
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| Abstract: | Human serum heme–albumin (HSA-heme-Fe) displays globin-like properties. Here, kinetics of O2-mediated oxidation of ferrous nitrosylated HSA-heme-Fe (HSA-heme-Fe(II)-NO) is reported. Values of the first-order rate constants for O2-mediated oxidation of HSA-heme-Fe(II)-NO (i.e., for ferric HSA-heme-Fe formation) and for NO dissociation from HSA-heme-Fe(II)-NO (i.e., for NO replacement by CO) are k = 9.8 × 10−5 and 8.3 × 10−4 s−1, and h = 1.3 × 10−4 and 8.5 × 10−4 s−1, in the absence and presence of rifampicin, respectively, at pH = 7.0 and T = 20.0 °C. The coincidence of values of k and h indicates that NO dissociation represents the rate limiting step of O2-mediated oxidation of HSA-heme-Fe(II)-NO. Mixing HSA-heme-Fe(II)-NO with O2 does not lead to the formation of the transient adduct(s), but leads to the final ferric HSA-heme-Fe derivative. These results reflect the fast O2-mediated oxidation of ferrous HSA-heme-Fe and highlight the role of drugs in modulating allosterically the heme-Fe-atom reactivity. |
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| Keywords: | Abbreviations: heme-Fe(III), ferric heme-Fe HSA, human serum albumin HSA-heme-Fe, human serum heme&ndash albumin HSA-heme-Fe(II), ferrous HSA-heme-Fe HSA-heme-Fe(II)-CO, ferrous carbonylated HSA-heme-Fe HSA-heme-Fe(II)-O2, ferrous oxygenated HSA-heme-Fe HSA-heme-Fe(II)-NO, ferrous nitrosylated HSA-heme-Fe HSA-heme-Fe(III), ferric HSA-heme-Fe Hb(II)-NO, ferrous nitrosylated hemoglobin HPX-heme-Fe(II)-NO, ferrous nitrosylated hemopexin-heme HPX-heme-Fe(III), ferric hemopexin-heme HPX-heme-Fe(III)-N(O)OO, peroxynitrite-bound ferric hemopexin-heme Mb(II)-NO, ferrous nitrosylated myoglobin Mb(III), ferric myoglobin Mb(III)-OONO, peroxynitrite-bound ferric myoglobin Ngb(II)-NO, ferrous nitrosylated neuroglobin Ngb(III), ferric neuroglobin |
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