Human serum heme-albumin (HSA-heme-Fe) displays globin-like properties. Here, kinetics of O(2)-mediated oxidation of ferrous nitrosylated HSA-heme-Fe (HSA-heme-Fe(II)-NO) is reported. Values of the first-order rate constants for O(2)-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 O(2)-mediated oxidation of HSA-heme-Fe(II)-NO. Mixing HSA-heme-Fe(II)-NO with O(2) 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 O(2)-mediated oxidation of ferrous HSA-heme-Fe and highlight the role of drugs in modulating allosterically the heme-Fe-atom reactivity.

O2-mediated oxidation of ferrous nitrosylated human serum heme-albumin is limited by nitrogen monoxide dissociation.

FASANO, MAURO
2011

Abstract

Human serum heme-albumin (HSA-heme-Fe) displays globin-like properties. Here, kinetics of O(2)-mediated oxidation of ferrous nitrosylated HSA-heme-Fe (HSA-heme-Fe(II)-NO) is reported. Values of the first-order rate constants for O(2)-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 O(2)-mediated oxidation of HSA-heme-Fe(II)-NO. Mixing HSA-heme-Fe(II)-NO with O(2) 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 O(2)-mediated oxidation of ferrous HSA-heme-Fe and highlight the role of drugs in modulating allosterically the heme-Fe-atom reactivity.
http://dx.doi.org/10.1016/j.bbrc.2011.02.005
Heme; metabolism, Humans, Iron; metabolism, Nitric Oxide; metabolism, Oxidation-Reduction, Oxygen; metabolism, Serum Albumin; metabolism
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11383/1722181
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