Arthropod oxygen transport

Copper is essential in animal metabolism. In some animals, such as the octopus and certain arthropods, it transports oxygen through the blood, a role performed by iron in mammals. As a result, the blood of these animals is green rather than red. In mammals, copper-bearing enzymes are necessary for healthy nerves and connective tissue. 

Oxygen transport (binuclear) Hemocyanin Mollusks and arthropods Dioxygen transport... 

Like hemerythrin, hemocyanin is an oxygen transport non-heme-containing protein found in some arthropods and molluscs (104,105). In the 02-bound form, hemocyanin contains an antiferromagnetically coupled binuclear copper(II) system (106) ligated by histidine residues, with a sideways / 2-v2 V2 peroxo group bound to both Cu11 centers (104), which superseded the previous model (107). 

Occurrence of hemocyanin related proteins in organisms. While textbooks teU that Hes occm only in arthropods and molluscs, recently Hes were also found in other phyla. The velvet worms (Onychophora) are considered living fossils and are closely related to the Euarthropoda. Onychophora possess a tracheal system for respiratory function, thus oxygen transport proteins have been considered unnecessary. In the hemolymph of the Epiperipatus sp. (Onychophora Peripatidae), an arthropod-type hemocyanin was found, demonstrating that such proteins exist outside the Euarthropoda. ... 

This similarity in spectral properties implies that haemocyanins should also have catalytic activity. From the available body of experimental data, it is clear that the distinction between the two major functions — oxygen transport and enzymatic activity — is determined by the presence or absence of a protein domain covering the active site. In the case of tyrosinase and catechol oxidase, inactive pro-enzyme forms are activated by removal of an amino acid which blocks the entrance channel to the active site (indicated by the black bar in Figure 14.7). Haemocyanins behave as silent inactive enzymes but can be activated in the same way if the blocking amino acid is removed. In arthropods, like crabs, this is located in the N-terminal domain of a subunit whereas in molluscs, like octopus, it is in the C-terminal domain of a functional unit. 

The hemocyanins are the oxygen-transport proteins of the three largest classes of mollusks (e.g., snails and squids), and of arthropods (e.g., spiders and scorpions). Mollusk and arthropod hemocyanin resemble each other in function... 

The VBCI model has been employed for the interpretation of the optical absorption and CD spectra of of peroxo bridged Cu dimers like oxy-Hemocyanin and corresponding small-molecule analogs (Figure 3).i "i 44-26 Hemocyanin (He), the oxygen-transport protein of mollusks and arthropods, contains a binuclear Cu(I) active site that reversibly binds dioxygen as peroxide in a... 

Most of the synthetic models we found in our literature survey are concerned with hemocyanine, the oxygen transport protein in arthropods and molluscs, and tyrosinase, which catalyzes the two-electron oxidation of phenolic compounds. Both proteins contain a coupled binuclear copper active site, a Type III copper centre,"which reversibly binds dioxygen as peroxide bridging between the two copper ions" [153]. The Cu-Cu distance is of the order of 300-400 pm, and a tetragonal coordination is achieved with donor nitrogen atoms of imidazole ligands from histidine [142]. 

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