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Animal heme-dependent peroxidases

Animal haem peroxidase
Symbol An_peroxidase
Pfam PF03098
InterPro IPR002007
SCOP 1mhl
OPM family 37
OPM protein 1q4g
Available PDB structures:

1mhlA:171-270 1dnuC:279-721 1d7wC:279-721 1d2vA:171-270 1dnwA:171-270 1cxpD:279-721 1d5lA:171-270 1mypD:280-721 1v0xA:450-507 1pxxB:450-507 3pghA:450-507 4coxD:450-507 1ddxC:450-507 5coxC:450-507 1cvuA:450-507 6coxB:450-507 1dd0A:450-507 1cx2C:450-507 1dcxA:450-507 1pgfB:131-583 1pgeA:131-583 1igzA:131-586 1pthA:131-583 1prhB:131-586 1q4gB:131-584 1pggA:131-583 1ht8A:131-583 1ebvA:131-583 1fe2A:131-586 1ht5B:131-583 1eqhB:131-586 1cqeB:131-586 2aylB:131-584 1diyA:131-584 1igxA:131-586 1u67A:131-586 1eqgA:131-586 1djjA:131-583

Animal heme-dependent peroxidases is a family of peroxidases.

Peroxidases are found in bacteria, fungi, plants and animals. On the basis of sequence similarity, a number of animal haem peroxidases can be categorised as members of a superfamily: myeloperoxidase (MPO); eosinophil peroxidase (EPO); lactoperoxidase (LPO); thyroid peroxidase (TPO); prostaglandin H synthase (PGHS); and peroxidasin[1][2][3].



Myeloperoxidase (MPO) plays a major role in the oxygen-dependent microbicidal system of neutrophils. EPO from eosinophilic granulocytes participates in immunological reactions, and potentiates tumor necrosis factor (TNF) production and hydrogen peroxide release by human monocyte-derived macrophages[4][5]. In the main, MPO (and possibly EPO) utilises Cl-ions and H2O2 to form hypochlorous acid (HOCl), which can effectively kill bacteria or parasites. In secreted fluids, LPO catalyses the oxidation of thiocyanate ions (SCN-) by H2O2, producing the weak oxidising agent hypothiocyanite (OSCN-), which has bacteriostatic activity[6]. TPO uses I- ions and H2O2 to generate iodine, and plays a central role in the biosynthesis of thyroid hormones T(3) and T(4).


3D structures of MPO and PGHS have been reported. MPO is a homodimer: each monomer consists of a light (A or B) and a heavy (C or D) chain resulting from post-translational excision of 6 residues from the common precursor. Monomers are linked by a single inter-chain disulphide. Each monomer includes a bound calcium ion[7]. PGHS exists as a symmetric dimer, each monomer of which consists of 3 domains: an N-terminal epidermal growth factor (EGF) like module; a membrane-binding domain; and a large C-terminal catalytic domain containing the cyclooxygenase and the peroxidase active sites. The catalytic domain shows striking structural similarity to MPO.

Active site

The cyclooxygenase active site, which catalyses the formation of prostaglandin G2 (PGG2) from arachidonic acid, resides at the apex of a long hydrophobic channel, extending from the membrane-binding domain to the centre of the molecule. The peroxidase active site, which catalyses the reduction of PGG2 to PGH2, is located on the other side of the molecule, at the haem binding site[8]. Both MPO and the catalytic domain of PGHS are mainly alpha-helical, 19 helices being identified as topologically and spatially equivalent; PGHS contains 5 additional N-terminal helices that have no equivalent in MPO. In both proteins, three Asn residues in each monomer are glycosylated.

Human proteins containing this domain



  1. ^ Nelson RE, Fessler LI, Takagi Y, Blumberg B, Keene DR, Olson PF, Parker CG, Fessler JH (1994). "Peroxidasin: a novel enzyme-matrix protein of Drosophila development". EMBO J. 13 (15): 3438-3447. PMID 8062820.
  2. ^ Poulos TL, Li H (1994). "Structural variation in heme enzymes: a comparative analysis of peroxidase and P450 crystal structures". Structure 2 (6): 461-464. PMID 7922023.
  3. ^ Kimura S, Ikeda-Saito M (1988). "Human myeloperoxidase and thyroid peroxidase, two enzymes with separate and distinct physiological functions, are evolutionarily related members of the same gene family". Proteins 3 (2): 113-120. PMID 2840655.
  4. ^ Kimura S, Hong YS, Kotani T, Ohtaki S, Kikkawa F (1989). "Structure of the human thyroid peroxidase gene: comparison and relationship to the human myeloperoxidase gene". Biochemistry 28 (10): 4481-4489. PMID 2548579.
  5. ^ Spessotto P, Dri P, Bulla R, Zabucchi G, Patriarca P (1995). "Human eosinophil peroxidase enhances tumor necrosis factor and hydrogen peroxide release by human monocyte-derived macrophages". Eur. J. Immunol. 25 (5): 1366-1373. PMID 7774640.
  6. ^ Wever R, Kast WM, Kasinoedin JH, Boelens R (1982). "The peroxidation of thiocyanate catalysed by myeloperoxidase and lactoperoxidase". Biochim. Biophys. Acta 709 (2): 212-219. PMID 6295491.
  7. ^ Fenna RE, Zeng J (1992). "X-ray crystal structure of canine myeloperoxidase at 3 A resolution". J. Mol. Biol. 226 (1): 185-207. PMID 1320128.
  8. ^ Picot D, Loll PJ, Garavito RM (1994). "The X-ray crystal structure of the membrane protein prostaglandin H2 synthase-1". Nature 367 (6460): 243-249. PMID 8121489.

This article includes text from the public domain Pfam and InterPro IPR002007

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Animal_heme-dependent_peroxidases". A list of authors is available in Wikipedia.
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