haptoglobin(HP) Homo sapiens 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. The protein encoded also exhibits antimicrobial activity against bacteria. A similar duplicated gene is located nexcaution:Although homologous to serine proteases, it has lost all essential catalytic residues and has no enzymatic activity.,function: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.,online information:Haptoglobin entry,online information:The Singapore human mutation and polymorphism database,polymorphism:In the human populations there are two major allelic forms, alpha-1 with 83 residues and alpha-2 with 142 residues. These alleles determine the 3 major phenotypes HP*1F/HP*1S and HP*2FS. The two main alleles of HP*1 are called HP*1F (fast) and HP*1S (slow).,similarity:Belongs to the peptidase S1 family.,similarity:Contains 1 peptidase S1 domain.,similarity:Contains 1 Sushi (CCP/SCR) domain.,similarity:Contains 2 Sushi (CCP/SCR) domains.,subunit:Tetramer of two alpha and two beta chains.,tissue specificity:Expressed by the liver and secreted in plasma.,tissue specificity:In adult liver the amount of HPR mRNA is at the lower limit of detection, therefore the extent of its expression is at most less than 1000-fold that of the HP1F gene. No HPR mRNA can be detected in fetal liver. Expressed in hepatoma G2 and leukemia molt-4 cell lines.,