Proteins copper and

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

Ruggiero, C.E., Carrier, S.M. and Tolman W.B. (1994) Reductive disproportionation of NO mediated by copper complexes Modeling N20 generation by copper proteins and heterogeneous catalysts, Angew. Chem. Int. Ed., 33, 895. 

Some Copper Proteins and Enzymes Localisation and Function Protein or Enzyme Localisation Function... 

Malmstrom, B.G., and Vanngard, T. 1960. Electron spin resonance of copper proteins and some model complexes. Journal of Molecular Biology 2 118-124. 

Reinhammar B (1984) Laccase. In Lontie R (ed) Copper proteins and copper enzymes, vol 3. CRC, Boca Raton, pp 1-36... 

Seven reviews (1984) In Lontie R (ed) Copper Proteins and Copper Enzymes, vol 1, CRC, Florida (USA)... 

Copper, Cu (d °), Cu " (d ) 4, tetrahedral Y-Thiolate, thioether, A-imidazoIe Electron transfer in Type I bine copper proteins and Type III heme-copper oxidases (Cua in cytochrome c oxidase, for example)... 

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. 

There are a number of excellent sources of information on copper proteins notable among them is the three-volume series Copper Proteins and Copper Enzymes (Lontie, 1984). A review of the state of structural knowledge in 1985 (Adman, 1985) included only the small blue copper proteins. A brief review of extended X-ray absorption fine structure (EXAFS) work on some of these proteins appeared in 1987 (Hasnain and Garner, 1987). A number of new structures have been solved by X-ray diffraction, and the structures of azurin and plastocyanin have been extended to higher resolution. The new structures include two additional type I proteins (pseudoazurin and cucumber basic blue protein), the type III copper protein hemocyanin, and the multi-copper blue oxidase ascorbate oxidase. Results are now available on a copper-containing nitrite reductase and galactose oxidase. 

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). 

Lontie, R., ed. (1984. Copper Proteins and Copper Enzymes, Vols. I-III. CRC Press, Boca Raton, Florida. 

Underwood, E. J. (1977). Trace Elements in Human and Animal Nutrition, 14th Ed. Academic Press, New York. [Quoted in Ettinger, M. J. (1984). In Copper Proteins and Copper Enzymes (R. Lontie, ed.), Vol. Ill, pp. 175-229. CRC Press, Boca Raton, Florida.]... 

Weser, U., Hartmann, H. J. Copper thiolate proteins (metallothionein), Copper proteins and copper enzymes, Vol. 3, p. 151, Boca Raton, CRC press 1984... 

Ruggiero, C. E., Carrier, S. M., Antholine, W. E., Whittaker, J. W., Cramer, C. J., and Tolman, W. B. (1993). Synthesis and structure and spectroscopic characterization of mononuclear copper nitrosyl complexes Models for nitric oxide adducts of copper proteins and copper exchange zeolites. J. Am. Chem. Soc. 115, 11285-11298. 

The expression for the contribution to the spin-orbit induced MCD intensity from perturbation of the ground state is somewhat reminiscent of an expression for the Ag quantity of EPR spectroscopy. The similarity lies in the paramagnetic term, Agp. This term is composed of integrals of a spin-orbit operator over molecular orbitals similar to the expression for the perturbation of the ground state in the presence of spin-orbit coupling (Eqs. 52-56). The paramagnetic contribution to Ag dominates for blue copper proteins and it was suspected that the MCD parameters and Amay have some sort of relationship. It was found that many of the terms that make large contributions to AgP do play a role in the MCD intensity but no simple relationship was found (160). 

Table I lists isomorphous replacements for various metalloproteins. Consider zinc enzymes, most of which contain the metal ion firmly bound. The diamagnetic, colorless zinc atom contributes very little to those physical properties that can be used to study the enzymes. Thus it has become conventional to replace this metal by a different metal that has the required physical properties (see below) and as far as is possible maintains the same activity. Although this aim may be achieved to a high degree of approximation [e.g., replacement of zinc by cobalt(II)], no such replacement is ever exact. This stresses the extreme degree of biological specificity. The action of an enzyme depends precisely on the exact metal it uses, stressing again the peculiarity of biological action associated with the idiosyncratic nature of active sites. (The entatic state of the metal ion is an essential part of this peculiarity.) Despite this specificity, the replacement method has provided a wealth of information about proteins that could not have been obtained by other methods. Clearly, there will often be a compromise in the choice of replacement. Even isomorphous replacement that should retain structure will not necessarily retain activity at all. However, it has become clear that substitutions can be made for structural studies where the substituted protein is inactive (e.g., in the copper proteins and the iron-sulfur proteins). It is also possible to substitute into metal coenzymes. Many studies have been reported of the...

Cass, A. E, G., Hill, H. A. O. Copper proteins and copper enzymes. In Biological Roles of Copper, Ciba Foundation Symposium 79, Amsterdam-Oxford-New York, Excerpta Medica, 1981, in press... 

Iron and copper in wines may form complexes with other components to produce deposits or clouds in white wines. Iron clouds generally occur at a pH range from 2.9 to 3.6 and are often controlled by adding citric acid to the wines (2). Copper clouds appear in wines when high levels of copper and sulfur dioxide exist and are a combination of sediments, protein-tannin, copper-protein, and copper-sulfur complexes (169). Further, the browning rate of white wines increases in the presence of copper and iron (143). The results of this study indicate that iron increased the browning rate more than copper. 

Copper is a necessary trace clement in animal metabolism. The human adult requirement is 2 milligrams per day. and the adult human body contains 100-150 milligrams of copper, die greatest concentrations existing in the liver and bones. Blood contains a number of copper proteins, and copper is known to be necessary lor the synthesis of hemoglobin, although there is no copper in the hemoglobin molecule. 

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