Abstract
Glutathionyl hemoglobin is a minor form of hemoglobin with intriguing properties. The measurement of the redox potential of its reactive β-93-Cysteine is useful to improve understanding of the response of erythrocytes to transient and chronic conditions of oxidative stress, where the level of glutathionyl hemoglobin is increased. An independent literature experiment describes the recovery of human erythrocytes exposed to an oxidant burst by measuring glutathione, glutathione disulfide and glutathionyl hemoglobin in a two-hour period. This article calculates a value for the redox potential E0 of the β-93-Cysteine, considering the erythrocyte as a closed system at equilibrium described by the Nernst equation and using the measurements of the literature experiment. The obtained value of E0 of −121 mV at pH 7.4 places hemoglobin as the most oxidizing thiol of the erythrocyte. By using as synthetic indicators of the concentrations the electrochemical potentials of the two main redox pairs in the erythrocytes, those of glutathione–glutathione disulfide and of glutathionyl–hemoglobin, the mechanism of the recovery phase can be hypothesized. Hemoglobin acts as the redox buffer that scavenges oxidized glutathione in the oxidative phase and releases it in the recovery phase, by acting as the substrate of the NAD(P)H-cofactored enzymes.
Highlights
The red blood cell (RBC), or erythrocyte, is the most abundant single cell type in the human organism and is essential to deliver atmospheric oxygen to the most remote districts of the body
The complete experiment was performed on RBCs taken both from humans and from rats
One important biochemical scenario is the mechanism whereby the RBC exposed to there is a sparing of soluble glutathione theresulting reducedoxidative form due to the of a burst of a radical-generating substance copes withinthe stress andreaction reglutathione sulfinic acid with the five-to-tenfold excess of can hemoglobin in the RBC, a covers to the previous condition
Summary
The red blood cell (RBC), or erythrocyte, is the most abundant single cell type in the human organism and is essential to deliver atmospheric oxygen to the most remote districts of the body. 120 days of existence of the cells For this reason, the RBC contains a multi-component anti-oxidant system aimed at quenching the off-products of oxygen activation and their reaction products with the organic molecules and biomolecular structures. Glutathionylated human hemoglobin (HbSSG) is a minor form of hemoglobin that carries a glutathione (γECG) linked through a disulfide (R1 CS-SCR2 ) bond to the thiol group of a cysteine residue, mainly characterized as the β-93 C in a single beta-chain of the tetramer. This form of hemoglobin was first highlighted in 1962 [1] and further characterized in 1986 [2,3,4] as a form that inhibits the polymerization of the sickle-cell Hb-S mutated form
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