Hemocyanin copper

Hemiterpenoids, 24 483 Hemizygous transgenics, 12 456 Hemocyanin, copper containing, 7 776 Hemodiafiltration (HDF), 26 832-833 Hemodialysis, 16 20 26 813-835 cellulosic fibers in, 16 18-19 dialyzer design and performance,... 

Figure 7. Structural aspects of purple hemocyanin. Coppers in the circles marked with dots illustrate different coordination geometry from those in the black circles, and shaded parts indicate the slightly deformed active site of oxyhemocyanin.

Copper is an essential element, being active in many enzymes and hemocyanin. Copper is an essential nutrient element to animals and plants. However, high Cu accumulation in animals and plants can be toxic. Copper is found in three oxidation states including cupric (+2), cuprous (+1), and elemental Cu (0). Cu+ and Cu + are the most important forms and are involved in oxidation-reduction reactions in soils and sediments (Figure 12.7). Cu+ and Cu + can exist in aqueous systems, although the latter is much more dominant. Copper is widely distributed in nature in its elemental state and in the form of sulfide, arsenite, chloride, and carbonates. The earth s crust on an average contains approximately 50 ppm copper. Soil and sediment contain approximately... 

Copper is one of the twenty-seven elements known to be essential to humans (69—72) (see Mineral nutrients). The daily recommended requirement for humans is 2.5—5.0 mg (73). Copper is probably second only to iron as an oxidation catalyst and oxygen carrier in humans (74). It is present in many proteins, such as hemocyanin [9013-32-3] galactose oxidase [9028-79-9] ceruloplasmin [9031 -37-2] dopamine -hydroxylase, monoamine oxidase [9001-66-5] superoxide dismutase [9054-89-17, and phenolase (75,76). Copper aids in photosynthesis and other oxidative processes in plants. 

Truchot, J.P. and F. Boitel. 1992. In vitro and in vivo effects of copper on hemocyanin-02 binding in the shore crab, Carcinus maenas. Comp. Biochem. Physiol. 103C 339-343. 

Table 5.2 contains data about selected copper enzymes from the references noted. It should be understood that enzymes from different sources—that is, azurin from Alcaligenes denitrificans versus Pseudomonas aeruginosa, fungal versus tree laccase, or arthropodan versus molluscan hemocyanin—will differ from each other to various degrees. Azurins have similar tertiary structures—in contrast to arthropodan and molluscan hemocyanins, whose tertiary and quaternary structures show large deviations. Most copper enzymes contain one type of copper center, but laccase, ascorbate oxidase, and ceruloplasmin contain Type I, Type II, and Type III centers. For a more complete and specific listing of copper enzyme properties, see, for instance, the review article by Solomon et al.4... 

This discussion of copper-containing enzymes has focused on structure and function information for Type I blue copper proteins azurin and plastocyanin, Type III hemocyanin, and Type II superoxide dismutase s structure and mechanism of activity. Information on spectral properties for some metalloproteins and their model compounds has been included in Tables 5.2, 5.3, and 5.7. One model system for Type I copper proteins39 and one for Type II centers40 have been discussed. Many others can be found in the literature. A more complete discussion, including mechanistic detail, about hemocyanin and tyrosinase model systems has been included. Models for the blue copper oxidases laccase and ascorbate oxidases have not been discussed. Students are referred to the references listed in the reference section for discussion of some other model systems. Many more are to be found in literature searches.50... 

---