Hemoglobin (deoxyhemoglobin) and myoglobin (deoxymyoglobin) (Hemoglobin (Hb), Myoglobin (Mb))

Deoxyhemoglobin and deoxymyoglobin refer to the forms of hemoglobin and myoglobin that are *not bound to oxygen*. Hemoglobin is a tetrameric protein present in red blood cells, responsible for transporting oxygen from lungs to tissues and returning carbon dioxide from tissues to lungs. Myoglobin is a monomeric protein found in muscle, facilitating oxygen storage and diffusion in tissues with high oxygen demand. Both contain a heme prosthetic group with a central iron atom that reversibly binds oxygen; in the deoxy (reduced) state, iron is not coordinated to oxygen, and key structural changes affect protein conformation and affinity for oxygen. Their deoxy forms are physiologically important for oxygen loading and unloading, with hemoglobin exhibiting cooperative binding properties essential for efficient oxygen delivery (the "Bohr effect"). While not direct drug targets, their functional impairment underlies important clinical conditions such as anemia, hemoglobinopathies, and toxicologic emergencies.

Other names

Hemoglobin (Hb)Deoxyhemoglobin (unoxygenated hemoglobin)Reduced hemoglobinMyoglobin (Mb)Deoxymyoglobin (unoxygenated myoglobin)Globin, hemoprotein

For carbon monoxide: competitive binding to the heme iron, preventing O₂ binding, leading to hypoxic injury. For cyanide: blocks electron transport, interferes with oxidative metabolism via heme-containing enzymes. Nitric oxide: physiological signaling, modulates blood pressure via hemoglobin interactions.