This gene encodes a preproprotein, which is processed to yield both alpha and beta chains, which subsequently combine as a tetramer to produce haptoglobin. Haptoglobin functions to bind free plasma hemoglobin, which allows degradative enzymes to gain access to the hemoglobin, while at the same time preventing loss of iron through the kidneys and protecting the kidneys from damage by hemoglobin. Mutations in this gene and/or its regulatory regions cause ahaptoglobinemia or hypohaptoglobinemia. This gene has also been linked to diabetic nephropathy, the incidence of coronary artery disease in type 1 diabetes, Crohn's disease, inflammatory disease behavior, primary sclerosing cholangitis, susceptibility to idiopathic Parkinson's disease, and a reduced incidence of Plasmodium falciparum malaria. A similar duplicated gene is located next to this gene on chromosome 16. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]

HP: Haptoglobin combines with free plasma hemoglobin, preventing loss of iron through the kidneys and protecting the kidneys from damage by hemoglobin, while making the hemoglobin accessible to degradative enzymes. Defects in HP are the cause of anhaptoglobinemia (AHP). AHP is a condition characterized by the absence of the serum glycoprotein haptoglobin. Serum levels of haptoglobin vary among normal persons: levels are low in the neonatal period and in the elderly, differ by population, and can be influenced by environmental factors, such as infection. Secondary hypohaptoglobinemia can occur as a consequence of hemolysis, during which haptoglobin binds to free hemoglobin. Belongs to the peptidase S1 family.

Protein type: Secreted, signal peptide; Secreted

Chromosomal Location of Human Ortholog: 16q22.2

Cellular Component: extracellular space; extracellular region

Molecular Function: antioxidant activity; protein binding; hemoglobin binding; catalytic activity

Biological Process: receptor-mediated endocytosis; response to hydrogen peroxide; metabolic process; immune system process; negative regulation of oxidoreductase activity; defense response to bacterium; acute-phase response; defense response

Disease: Anhaptoglobinemia