Hemopexin precursor, also known as HPX, is a serum glycoprotein that binds heme and transports it to the liver for breakdown and iron recovery, after which the free hemopexin returns to the circulation. It is expressed by the liver and is secreted in plasma. Hemopexin may play a role in the maintenance of metal ion homeostasis. HPX can also act as a toxic protease that leads to proteinuria and glomerular alterations, which are characteristics of minimal changes disease (MCD), a common cause of nephrotic syndrome. Recombinant human HPX protein, fused to His-tag at N-terminus, was expressed in E.coli.