Binding and redox reaction kinetic studies of native and modified hemoglobins with haptoglobin

Monday, October 24, 2011 — Poster Session I
Noon – 2:00 p.m.	Natcher Conference Center	FDA/CBER	BIOCHEM/CHEM-10

Authors

• Y Jia
• S Banerjee
• C Siburt
• A Crumbliss
• A Alayash

Abstract

Kinetic measurements revealed that beta beta cross-linked Hb binds to Hp with lower affinity than that of native Hb, whereas the alpha alpha cross-linked Hb showed little or no binding activities. The binding of Hp increased oxygen binding affinity, accelerated the oxidative reactions of native Hb with nitrite, and stabilized the ferryl Hb formed in the presence of H2O2. In contrast, Hp had no effects on the reactions of alpha alpha cross-linked Hb with these ligands. Similarly no differences were seen in the redox reactions of native and modified Hbs, including autoxidation, metHb oxidation by H2O2, NO dioxygenation, ferryl Hb stabilization and heme degradation by H2O2, in the presence or absence of Hp. Interestingly, the spectroelectrochemistry experiments on native Hb and beta cross-linked Hb bound to Hp showed a shift of the reduction potentials towards more negative values by 70 and 54 mV respectively [Vs. NHE] with respect to the redox values of free Hb and beta cross-linked Hb under identical conditions. These studies show that Hp may be used in the clearance and oxidative inactivation of native Hb and beta cross-linked Hb to counter the toxicity of some oxygen therapeutics and with free Hb in hemolytic anemias.

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