Hemopexin

Hemopexin is a plasma glycoprotein synthesized primarily by the liver. It is the protein with the highest affinity for heme (ferriprotoporphyrin IX), a porphyrin ring containing iron that is released during the breakdown of hemoglobin.

Hemopexin's primary function is to bind free heme released into the circulation. By binding heme, hemopexin prevents the iron within the heme molecule from catalyzing oxidative reactions that can damage tissues. The hemopexin-heme complex is then internalized by hepatocytes (liver cells) via receptor-mediated endocytosis, allowing the iron to be salvaged and recycled, and the porphyrin ring to be metabolized. The receptor involved in this process is the LDL receptor-related protein 1 (LRP1).

In addition to its role in heme scavenging, hemopexin also exhibits anti-inflammatory properties and may contribute to the regulation of the immune system. Its concentration in plasma can be influenced by various factors, including inflammation, hemolysis (red blood cell destruction), and liver function.

Measurement of hemopexin levels in blood can be used clinically. Low levels of hemopexin can indicate increased hemolysis, as the protein is being consumed in the process of binding free heme. Hemopexin levels may also be affected by liver disease. Increased levels may be observed in certain inflammatory conditions.

The gene encoding hemopexin is located on human chromosome 11.