Reductive nitrosylation of ferric human serum heme-albumin.
Heme endows human serum albumin (HSA) with heme-protein-like reactivity and spectroscopic properties. Here, the kinetics and thermodynamics of reductive nitrosylation of ferric human serum heme-albumin [HSA-heme-Fe(III)] are reported. All data were obtained at 20 degrees C. At pH 5.5, HSA-heme-Fe(III) binds nitrogen monoxide (NO) reversibly, leading to the formation of nitrosylated HSA-heme-Fe(III) [HSA-heme-Fe(III)-NO]. By contrast, at pH >or= 6.5, the addition of NO to HSA-heme-Fe(III) leads to the transient formation of HSA-heme-Fe(III)-NO in equilibrium with HSA-heme-Fe(II)-NO(+). Then, HSA-heme-Fe(II)-NO(+) undergoes nucleophilic attack by OH(-) to yield ferrous human serum heme-albumin [HSA-heme-Fe(II)]. HSA-heme-Fe(II) further reacts with NO to give nitrosylated HSA-heme-Fe(II) [HSA-heme-Fe(II)-NO]. The rate-limiting step for reductive nitrosylation of HSA-heme-Fe(III) is represented by the OH(-)-mediated reduction of HSA-heme-Fe(II)-NO(+) to HSA-heme-Fe(II). The value of the second-order rate constant for OH(-)-mediated reduction of HSA-heme-Fe(II)-NO(+) to HSA-heme-Fe(II) is 4.4 x 10(3) M(-1) s(-1). The present results highlight the role of HSA-heme-Fe in scavenging reactive nitrogen species.
Ascenzi
Paolo
P
Department of Biology, University Roma Tre, Roma, Italy.
Cao
Yu
Y
di Masi
Alessandra
A
Gullotta
Francesca
F
De Sanctis
Giampiero
G
Fanali
Gabriella
G
Fasano
Mauro
M
Coletta
Massimo
M
D000818:Animals; D005290:Ferric Compounds / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006736:Horses; D006801:Humans; D007700:Kinetics; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D011817:Rabbits; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D050661:Sperm Whale; D013816:Thermodynamics
D005290:Ferric Compounds; D012709:Serum Albumin; D009569:Nitric Oxide; D006418:Heme