Linearity of the hemoglobin oxidation bohr effect

Area of Science:

• Biochemistry
• Physiological Chemistry
• Protein Chemistry

Background:

• The Bohr effect describes hemoglobin's (Hb) response to pH changes, influencing oxygen transport.
• Understanding Hb's proton linkage during oxidation is crucial for its allosteric function.
• Previous studies reported nonlinear proton release during Hb oxidation.

Purpose of the Study:

• To re-evaluate the hemoglobin oxidation Bohr effect.
• To identify the cause of previously reported nonlinear proton release.
• To assess the compatibility of existing Hb models with oxidation-linked proton release.

Main Methods:

• Re-analysis of hemoglobin oxidation data.
• Comparison of oxidation-linked proton release with heme ligation.
• Evaluation of published two-state allosteric transition models.

Main Results:

• The hemoglobin oxidation Bohr effect is linear with the fraction of hemes oxidized below pH 7.
• Nonlinear proton release reported previously is an artifact of ferricyanide use.
• Existing Hb allosteric models are incompatible with linear proton release upon oxidation.

Conclusions:

• Hemoglobin's proton release during oxidation is directly proportional to heme oxidation.
• Artifactual data obscured the true linear relationship, necessitating model revision.
• Accurate proton linkage schemes are essential for understanding hemoglobin's allosteric behavior.