Hemopexin from human plasma

HPX (hemopexin) is a 60kDa acute phase glycoprotein produced by various cell types, including, parenchymal cells of the liver, retinal ganglionic and photoreceptor cells, kidney mesangial cells, and central and peripheral nervous system cells.

Hemopexin is a single-chain protein belonging to the family of blood transport proteins. It binds to heme released into the bloodstream during the degradation process. Recent studies have demonstrated that hemopexin acts as an extracellular antioxidant against hemoglobin-mediated damage in inflammation. Hemopexin protects against heme toxicity and conserves and recycles iron. Abnormal levels of hemopexin are associated with hemolytic anemia, chronic neuromuscular disease, and acute intermittent porphyria.

HPX (hemopexin) has high affinity for heme and binds with it in equimolar amounts. It scavenges free heme, and this heme-HPX is taken up by liver by CD91 (cluster of differentiation)/LRP1 (low density lipoprotein receptor-related protein 1) receptor-mediated endocytosis. This process prevents tissue damage mediated by heme. It functions as a permeability factor in kidney and in steroid-sensitive nephrotic syndrome. In minimal change nephrotic syndrome, it might either be responsible for causing or prolonging glomerular permeability. In diabetic patients with diabetic macular edema (DME), this protein is overexpressed in retinal pigment epithelium (RPE), and HPX-mediated hyperpermeability is inhibited by dexamethasone. Therefore, HPX might be implicated in the pathogenesis of DME.

Lyophilized from 11.9 mM phosphate, 137 mM NaCl, 2.7 mM KCl, pH 7.4.