karbaminohemoglobiinina

Karbaminohemoglobina is a form of hemoglobin in which carbon dioxide binds to the protein part of Hb, the globin chains, at the N-terminal amino groups to form a carbamate. This binding occurs on the amino termini of the globin chains, not at the heme iron, and it is reversible.

Formation and transport: About 5–10 percent of circulating CO2 is carried as carbaminohemoglobin. CO2 binds more readily to deoxygenated Hb than to oxyhemoglobin, via the reaction Hb-NH2 + CO2 ⇌ Hb-NH-COO− + H+. The formation of carbaminohemoglobin also releases protons, which contributes to the Bohr effect and helps unload oxygen in tissues while loading CO2.

Release and physiology in the lungs: In the lungs, higher PO2 and lower CO2 shift the equilibrium toward CO2 release from Hb. The carbamino group dissociates, and the bound CO2 is exhaled. Concurrently, bicarbonate formed in red blood cells is converted back to CO2 by carbonic anhydrase and expelled, while the overall CO2 transport in blood is completed.

Physiological significance: Although the majority of CO2 is transported as bicarbonate, carbaminohemoglobin provides a reversible mechanism for CO2 transport that is linked to the oxygenation state of Hb. The interaction also contributes to the regulation of blood pH and the Bohr effect, aiding efficient gas exchange in tissues and lungs. The extent of carbamino formation varies with metabolic conditions and the exact composition of hemoglobin.