HP - Haptoglobin - human protein (Function)
 
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HP »  Haptoglobin
 
Protein also known as:  Zonulin. Cleaved into:  Haptoglobin alpha chain; Haptoglobin beta chain.
Gene name:  HP
Family name: Peptidase S1
Entry whose protein(s) existence is based on evidence at protein level
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GENE REF ISO

Function

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Overview 
Uncleaved haptoglogin, also known as zonulin, plays a role in intestinal permeability, allowing intercellular tight junction disassembly, and controlling the equilibrium between tolerance and immunity to non-self antigens.  
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  • CuratedUniProtKB
As a result of hemolysis, hemoglobin is found to accumulate in the kidney and is secreted in the urine. Haptoglobin captures, and combines with free plasma hemoglobin to allow hepatic recycling of heme iron and to prevent kidney damage. Haptoglobin also acts as an Antimicrobial; Antioxidant, has antibacterial activity and plays a role in modulating many aspects of the acute phase response. Hemoglobin/haptoglobin complexes are rapidely cleared by the macrophage CD163 scavenger receptor expressed on the surface of liver Kupfer cells through an endocytic lysosomal degradation pathway.  
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  • CuratedUniProtKB
GO molecular function 
Antioxidant activitydefinition[GO:0016209]  
  • IEAUniProtKB KW
Catalytic activitydefinition[GO:0003824] silver  
  • IEAInterPro 2 GO
Hemoglobin bindingdefinition[GO:0030492]  
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  • IDABHF-UCL
Protein bindingdefinition[GO:0005515]  
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  • IPIIntAct
GO biological process 
Acute-phase responsedefinition[GO:0006953]  
  • IEAUniProtKB KW
Defense responsedefinition[GO:0006952]  
1
  • TASPINC
Defense response to bacteriumdefinition[GO:0042742]  
  • IEAUniProtKB KW
Immune system processdefinition[GO:0002376]  
  • IEAUniProtKB KW
Metabolic processdefinition[GO:0008152]  
  • IEAInterPro 2 GO
Negative regulation of hydrogen peroxide catabolic processdefinition[GO:2000296]  
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  • IDABHF-UCL
Negative regulation of oxidoreductase activitydefinition[GO:0051354]  
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  • IDABHF-UCL
Positive regulation of cell deathdefinition[GO:0010942]  
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  • IDABHF-UCL
Response to hydrogen peroxidedefinition[GO:0042542]  
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  • IDABHF-UCL
Enzymatic activity 
 
More information is available from:
Pathways 
According to Reactome, this protein belongs to the following pathway:
Scavenging of heme from plasma  REACT_160163  
Caution 
Although homologous to serine proteases, it has lost all essential catalytic residues and has no enzymatic activity.  
  • CuratedUniProtKB
 

Keywords

Biological process 
Acute phase  definition   [KW-0011]
Immunity  definition   [KW-0391]
Molecular function 
Antibiotic  definition   [KW-0044]
Antimicrobial  definition   [KW-0929]
Antioxidant  definition   [KW-0049]
Serine protease homolog  definition   [KW-0721]
Technical term 
Reference proteome  definition   [KW-1185]
 

Further external links

GeneWiki: Haptoglobin
GenomeRNAi: 3240
PRO: PR:P00738