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The modification of hemoglobin by citrate
1Department of Biochemistry, University of Ottawa, Ontario, Canada.
The Journal of Biological Chemistry
|July 25, 1993
Summary
Citrate modification of hemoglobin, specifically its N-terminal valine residues, reduces oxygen binding cooperativity. This citrate-treated hemoglobin S also shows increased solubility and delayed sickling, offering potential therapeutic benefits.
Area of Science:
- Biochemistry
- Protein Chemistry
- Hematology
Background:
- Hemoglobin (Hb) is crucial for oxygen transport.
- Sickle cell disease (SCD) involves abnormal hemoglobin S (HbS).
- Modifying Hb structure can alter its properties and potentially treat SCD.
Purpose of the Study:
- To investigate the covalent modification of hemoglobin using citrate.
- To assess the impact of citrate modification on Hb's oxygen-binding properties.
- To evaluate the effect of citrate modification on HbS solubility and polymerization.
Main Methods:
- Activation of citrate with a water-soluble carbodiimide.
- Covalent modification of N-terminal valine residues on alpha- and beta-globin chains.
- Measurement of oxygen affinity (p50) and cooperativity.
- Assessment of HbS solubility and deoxygenation kinetics in phosphate solutions.
Main Results:
- Citrate specifically modifies N-terminal valine residues of hemoglobin at neutral pH.
- Citrate modification decreases the cooperativity of oxygen binding without altering p50.
- Citrate-modified HbS exhibits enhanced solubility and increased resistance to deoxygenation-induced aggregation.
Conclusions:
- Citrate is an effective agent for modifying hemoglobin's functional properties.
- Reduced cooperativity and increased HbS solubility suggest potential therapeutic applications for SCD.
- Citrate modification offers a novel approach to managing HbS polymerization and its associated pathologies.