Hemoglobin (Oxyhemoglobin form) (HbO₂)

Hemoglobin is a globular metalloprotein found in red blood cells responsible for transporting oxygen from the lungs to body tissues and facilitating carbon dioxide return from tissues back to the lungs. The molecule consists of four subunits—two alpha and two beta chains—each containing an iron-bearing heme group capable of binding one molecule of oxygen. When all four sites are occupied by O₂, it forms oxyhemoglobin—the main carrier form for nearly 98% of transported oxygen in human blood[3][4][7]. The binding process exhibits positive cooperativity; each successive O₂ molecule binds more easily after the first attaches due to conformational changes within the protein structure[1][3]. This reversible binding allows efficient loading in high-O₂ environments like lung alveoli and unloading where tissue demand increases. The transition between deoxy-, oxy-, carboxy-, and met forms underlies both normal physiology and several pathologies but does not make hemoglobin itself a classic "therapeutic target" such as an enzyme or receptor would be. Instead, its function is essential for life-supporting gas exchange processes[2][5]. Note on correctness: "Oxyhemoglobin" refers specifically to the oxygen-bound state of hemoglobin rather than an independent molecular entity or classical druggable target such as receptors/enzymes/transporters. Thus, it should not be classified as a canonical therapeutic target; instead, it represents one functional state within normal physiological cycling between deoxy-, oxy-, carboxy-, and met states.[6]

Other names

OxyhemoglobinOxygenated hemoglobinHbO₂

Not applicable; oxyhemoglobin is not a drug target but rather the oxygen-bound state of hemoglobin.