Haptoglobin (Hpt)

HP; Hp2-Alpha; Alpha-2-Macroglobulin; Zonulin

SPN	V994
HGNC	5141
MGI	96211
PubMed	15274115
RGD	2825
UniProt	P00738
Wiki	Haptoglobin

Haptoglobin is a protein that in humans is encoded by the HP gene. In blood plasma, haptoglobin binds free hemoglobin (Hb) released from erythrocytes with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen). In clinical settings, the haptoglobin assay is used to screen for and monitor intravascular hemolytic anemia. In intravascular hemolysis free hemoglobin will be released into circulation and hence haptoglobulin will bind the Hb. This causes a decline in Hp levels. Conversely, in extravascular hemolysis the reticuloendothelial system, especially splenic monocytes, phagocytose the erythrocytes and hemoglobin is not released into circulation and hence haptoglobulin levels are normal.

Reference

"Molecular cloning of human haptoglobin cDNA: evidence for a single mRNA coding for alpha 2 and beta chains."
EMBO J. 2:1003-1007(1983) [PubMed] [Europe PMC] [Abstract]

"Identification and characterization of human haptoglobin cDNA."
Proc. Natl. Acad. Sci. U.S.A. 80:5875-5879(1983) [PubMed] [Europe PMC] [Abstract]

"Characterization of human haptoglobin cDNAs coding for alpha 2FS beta and alpha 1S beta variants."
FEBS Lett. 168:103-107(1984) [PubMed] [Europe PMC] [Abstract]

"Evolution of haptoglobin: comparison of complementary DNA encoding Hp alpha 1S and Hp alpha 2FS."
Nucleic Acids Res. 12:4531-4538(1984) [PubMed] [Europe PMC] [Abstract]

"Structure and expression of the human haptoglobin locus."
EMBO J. 4:119-126(1985) [PubMed] [Europe PMC] [Abstract]

"Nucleotide sequence of the haptoglobin and haptoglobin-related gene pair. The haptoglobin-related gene contains a retrovirus-like element."
J. Biol. Chem. 260:6698-6709(1985) [PubMed] [Europe PMC] [Abstract]

"Junctions between genes in the haptoglobin gene cluster of primates."
Genomics 14:948-958(1992) [PubMed] [Europe PMC] [Abstract]

"Complete sequencing and characterization of 21,243 full-length human cDNAs."
Nat. Genet. 36:40-45(2004) [PubMed] [Europe PMC] [Abstract]

"The sequence and analysis of duplication-rich human chromosome 16."
Nature 432:988-994(2004) [PubMed] [Europe PMC] [Abstract]

"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)."
Genome Res. 14:2121-2127(2004) [PubMed] [Europe PMC] [Abstract]

"Expression of cloned human haptoglobin and alpha 1-antitrypsin complementary DNAs in Saccharomyces cerevisiae."
DNA 5:129-136(1986) [PubMed] [Europe PMC] [Abstract]

"Sequence of human haptoglobin cDNA: evidence that the alpha and beta subunits are coded by the same mRNA."
Nucleic Acids Res. 11:5811-5819(1983) [PubMed] [Europe PMC] [Abstract]

"Genome duplications and other features in 12 Mb of DNA sequence from human chromosome 16p and 16q."
Genomics 60:295-308(1999) [PubMed] [Europe PMC] [Abstract]

"Duplication within the haptoglobin Hp2 gene."
Nature 309:131-135(1984) [PubMed] [Europe PMC] [Abstract]

"Covalent structure of human haptoglobin: a serine protease homolog."
Proc. Natl. Acad. Sci. U.S.A. 77:3388-3392(1980) [PubMed] [Europe PMC] [Abstract]

"Protein analysis of human maculae in relation to age-related maculopathy."
Lab. Invest. 73:267-272(1995) [PubMed] [Europe PMC] [Abstract]

"Studies on the interchain disulfides of human haptoglobins."
Can. J. Biochem. 51:249-264(1973) [PubMed] [Europe PMC] [Abstract]

"Identification and quantification of N-linked glycoproteins using hydrazide chemistry, stable isotope labeling and mass spectrometry."
Nat. Biotechnol. 21:660-666(2003) [PubMed] [Europe PMC] [Abstract]

"Screening for N-glycosylated proteins by liquid chromatography mass spectrometry."
Proteomics 4:454-465(2004) [PubMed] [Europe PMC] [Abstract]

"Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry."
J. Proteome Res. 4:2070-2080(2005) [PubMed] [Europe PMC] [Abstract]

"Identification of N-linked glycoproteins in human saliva by glycoprotein capture and mass spectrometry."
J. Proteome Res. 5:1493-1503(2006) [PubMed] [Europe PMC] [Abstract]

"Glycoproteomics analysis of human liver tissue by combination of multiple enzyme digestion and hydrazide chemistry."
J. Proteome Res. 8:651-661(2009) [PubMed] [Europe PMC] [Abstract]

"A strategy for precise and large scale identification of core fucosylated glycoproteins."
Mol. Cell. Proteomics 8:913-923(2009) [PubMed] [Europe PMC] [Abstract]

"Enrichment of glycopeptides for glycan structure and attachment site identification."
Nat. Methods 6:809-811(2009) [PubMed] [Europe PMC] [Abstract]

"Identification of human zonulin, a physiological modulator of tight junctions, as prehaptoglobin-2."
Proc. Natl. Acad. Sci. U.S.A. 106:16799-16804(2009) [PubMed] [Europe PMC] [Abstract]

"Haptoglobin: basic and clinical aspects."
Antioxid. Redox Signal. 12:293-304(2010) [PubMed] [Europe PMC] [Abstract]

"Initial characterization of the human central proteome."
BMC Syst. Biol. 5:17-17(2011) [PubMed] [Europe PMC] [Abstract]

"Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer."
Physiol. Rev. 91:151-175(2011) [PubMed] [Europe PMC] [Abstract]

"Resveratrol-induced changes of the human adipocyte secretion profile."
J. Proteome Res. 11:4733-4743(2012) [PubMed] [Europe PMC] [Abstract]

"An enzyme assisted RP-RPLC approach for in-depth analysis of human liver phosphoproteome."
J. Proteomics 96:253-262(2014) [PubMed] [Europe PMC] [Abstract]

"A novel I247T missense mutation in the haptoglobin 2 beta-chain decreases the expression of the protein and is associated with ahaptoglobinemia."
Hum. Genet. 114:499-502(2004) [PubMed] [Europe PMC] [Abstract]