Hemocyanin

1ll1 :110-373 1hc1A:136-393 1hcyD:136-393 1hc6B:136-393 1hc4C:136-393 1hc3C:136-393 Hemocyanins (also spelled haemocyanins and abbreviated Hc) are proteins that transport oxygen throughout the bodies of some invertebrate animals.

[2] Hemocyanins are found in the Mollusca and Arthropoda, including cephalopods and crustaceans, and utilized by some land arthropods such as the tarantula Eurypelma californicum,[3] the emperor scorpion,[4] and the centipede Scutigera coleoptrata.

These proteins are involved in the process of sclerotization of arthropod cuticle, in wound healing, and humoral immune defense.

[9] The evolutionary changes within the phylogeny of the hemocyanin superfamily are closely related to the emergence of these different proteins in various species.

[10] Although the respiratory function of hemocyanin is similar to that of hemoglobin, there are a significant number of differences in its molecular structure and mechanism.

Each hemocyanin monomer holds a pair of copper(I) cations in place via interactions with the imidazole rings of six histidine residues.

In some hemocyanins of horseshoe crabs and some other species of arthropods, cooperative binding is observed, with Hill coefficients of 1.6–3.0.

Simple hexamers are found in the spiny lobster Panulirus interruptus and the isopod Bathynomus giganteus.

[1][19] Spectroscopy of oxyhemocyanin shows several salient features:[21] Much work has been devoted to preparing synthetic analogues of the active site of hemocyanin.

[21] One such model, which features a pair of copper centers bridged side-on by peroxo ligand, shows ν(O-O) at 741 cm−1 and a UV-Vis spectrum with absorbances at 349 and 551 nm.

[25] Keyhole limpet hemocyanin (KLH) is an immune stimulant derived from circulating glycoproteins of the marine mollusk Megathura crenulata.

Keyhole limpet hemocyanin inhibits growth of human Barrett's esophageal cancer through both apoptic and nonapoptic mechanisms of cell death.

The study compared oxyhemocyanin levels in the blood of white shrimp housed in an indoor pond with a commercial diet with that of white shrimp housed in an outdoor pond with a more readily available protein source (natural live food) as well.

The levels of these blood proteins and metabolites appear to be dependent on energetic demands and availability of those energy sources.

The 3.8 MDa structure of molluscan Japanese flying squid hemocyanin. It is a homodecamer of five dimers arranged into a 31 nm diameter cylinder. Each monomer has a string of eight individual subunits each with a Cu 2 O 2 binding site. [ 16 ] PDB : 4YD9 ​
A hemocyanin active site in the absence of O 2 (each Cu center is a cation, charges not shown).
O 2 -bound form of a hemocyanin active site (the Cu 2 center is a dication, charge not shown).
The underside of the carapace of a red rock crab ( Cancer productus ). The purple coloring is caused by hemocyanin.