Copper proteins compounds

MIO. Mann, T., and Keilin, D., Haemocuprein and hepatoouprein, copper-protein compounds of blood and liver of mammals. Proc. Roy. Soc. 126, 303-315 (1938). 

In addition to its infiuence on blood formation copper has been shown t( be concerned in many other functions within the body. A number of oxi dases which play a part in the oxidation-reduction processes of the cell are known to be copper-protein compounds. These include the polypheAol oxidases of mushrooms and potatoes and ascorbic acid oxidase. Cytochrome oxidase is also usually considered a copper compound, although this is not certain. It is generally believed that the copper ion is the reversibly attached prosthetic group of the enzyme whose activity is associated with a valency change of the copper. An adequate intake of copper has been shown to be essential for the formation and maintenance of normal cytochrome oxidase and catalase activity of certain tissues in the rat. ... 

Forms of Occurrence.—At least four derivatives are known turacin, a copper porphyrin found as a purple pigment in feathers hcemocuprin, obtained from hsemocyanin hcemocuprein, a copper-protein compound in red blood cells and serum and hepatocuprein, found in liver (Mann and Keilin, 1938). Less than half the copper in plants occurs in a water-soluble form, which suggests the existence of other organic derivatives. 

C20-0102. Blue copper proteins are blue when they contain Cu but colorless as Cu compounds. The color comes from an interaction in which a photon causes an electron to transfer from a sulfur lone pair on a cysteine iigand to the copper center. Why does this charge transfer interaction occur for Cu but not Cu+ ... 

Model systems for Type I copper proteins structures of copper coordination compounds with thioether and azole-containing ligands.17... 

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... 

Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds Wlley-Intersclence New York, 1986. Long, D. A. Raman Spectroscopy McGraw-Hill New York, 1977. Loehr, T. M. Sanders-Loehr, J. In Copper Proteins and Copper Enzymes Lontle, R., Ed. CRC Press Boca Raton, 1984 pp. 115-155. 

The multi-copper oxidases include laccase, ceruloplasmin, and ascorbate oxidase. Laccase can be found in tree sap and in fungi ascorbate oxidase, in cucumber and related plants and ceruloplasmin, in vertebrate blood serum. Laccases catalyze oxidation of phenolic compounds to radicals with a concomitant 4e reduction of O2 to water, and it is thought that this process may be important in the breakdown of lignin. Ceruloplasmin, whose real biological function is either quite varied or unknown, also catalyzes oxidation of a variety of substrates, again via a 4e reduction of O2 to water. Ferroxidase activity has been demonstrated for it, as has SOD activity. Ascorbate oxidase catalyzes the oxidation of ascorbate, again via a 4e reduction of O2 to water. Excellent reviews of these three systems can be found in Volume 111 of Copper Proteins and Copper Enzymes (Lontie, 1984). 

J. A Fee Copper Proteins - Systems Containing the Blue" Copper Center. - M.F.Dunn Mechanisms of Zinc Ion Catalysis in Small Molecules and Enzymes. - W. Schneider Kinetics and Mechanism of Metalloporphyrin Formation. - M. Orchin, D. M. Bollinger Hydro gen-Deuterium Exchange in Aromatic Compounds. 

A number of copper -containing protein compounds are enzymes with an oxidase function (ascorbic acid oxidase, urease, etc 1 and these play an important role in Ihe biological oxidation-reduction system. There is a definite relationship of copper with iron in connection with utilization of iron in hemoglobin function. 

Among the coordination compounds obtained on the basis of polypyrazolyl-borates, it is worth emphasizing the copper chelates 235 which are still the only biomimetic model of blue copper proteins, reproducing all their physical (UV-and EPR-spectral) properties [441,446-448], Compound 236 [449] is also an example of complexes of this kind of system ... 

Metal salts with other cations are synthesized in a similar manner. Among these studies, the obtaining of coordination compounds of copper(II) in methanol with N2S2 ligand environment should be mentioned. These complexes are of permanent interest due to the modeling of active centers of blue copper proteins on their basis (see Sec. 2.2.5.4) [235-237]. Such complexes were obtained, in particular, by interaction of divalent copper perchlorate and tetrafluoroborate with very exotic ligands 661 and 662 in methanol [238] ... 

The copper proteins containing the type 2 active site are also known as normal copper proteins, because their spectroscopic features are similar to those of common Cu coordination compounds. The copper ion in these proteins is surrounded by four N and/or O donor atoms in either square-planar or distorted tetrahedral geometry [3, 4]. Examples of proteins with this active site include... 

Type II copper proteins, or low blue copper proteins, have less intense colours at normal concentrations, but even low blue copper sites have quite high absorption coefficients when compared with simple copper(II) coordination compounds. Bovine erthyrocyte superoxide dismutase (BSOD) is an example of a low blue copper(II) protein with Xmax 680 nm (e = dm3 300 mol-1 cm-1). 

Recently several new active site model compounds have been prepared (Carrier et al., 1991) using sterically hindered tris(pyrazoyI)hydroborate (L) and tris(thioethyl)amine (L2) as ligands. The copper nitrite complex LCu11 (N02) models the enzyme substrate complex and X-ray studies confirm that the complex is tetrahedral. A mononuclear copper—nitrosyl complex similar to postulated NO adducts of copper proteins has also been prepared from LCu1 (MeCN) and NO, which has been tentatively identified as a Cu11 -NO species on the basis of IR (v NO 1711 cm 1) and ESR evidence. 

B(C2H5)2The tridentate ligand [HB pz-3,5-(CH3)2 2(SCgH4-4-CH3)]" was synthesized intentionally from ArSH and K[H2B pz-3,5-(CH3)2 2]- It was converted to L MSR complexes (M = Cu or Co SR = 0-ethylcysteine,p-nitrobenzenethiolate or pentafluorophenylthiolate). These compounds were studied as synthetic approximations of the proposed active sites in the blue copper proteins (plastocyanin, azurin)... 

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