Copper biological function

Copper is required for all forms of aerobic and most forms of anaerobic life. In humans, the biological function of copper is related to the enzymatic action of specific essential copper proteins (66). Lack of these copper enzymes is considered a primary factor in cerebral degeneration, depigmentation, and arterial changes. Because of the abundance of copper in most human diets, chemically significant copper deficiency is extremely rare (67). 

Cadmium occurs naturally as sulfide co-deposited with zinc, copper, and lead sulfides. It is produced as a by-product in above-mentioned metal processing. Similar to lead and mercury, this heavy metal has no known biological functions in living organisms, and accordingly its accumulation in food and water leads to undesirable consequences to biota. Cadmium toxicology is related to dangerous influence to CNS and excretion systems, firstly, on kidney. 

Metallothionein was first discovered in 1957 as a cadmium-binding cysteine-rich protein (481). Since then the metallothionein proteins (MTs) have become a superfamily characterized as low molecular weight (6-7 kDa) and cysteine rich (20 residues) polypeptides. Mammalian MTs can be divided into three subgroups, MT-I, MT-II, and MT-III (482, 483, 491). The biological functions of MTs include the sequestration and dispersal of metal ions, primarily in zinc and copper homeostasis, and regulation of the biosynthesis and activity of zinc metalloproteins. 

Most mechanisms which control biological functions, such as cell respiration and photosynthesis (already discussed in Chapter 5, Section 3.1), are based on redox processes. In particular, as shown again in Figure 1, it is evident that, based on their physiological redox potentials, in photosynthesis a chain of electron carriers (e.g. iron-sulfur proteins, cytochromes and blue copper proteins) provides a means of electron transport which is triggered by the absorption of light. 

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). 

Laccase, 36 318, 329, 40 122 see also Blue copper oxidases amino-acid sequences, 40 141 anaerobic reduction, 40 158-160 biological function, 40 124 electrochemistry, 36 360 fungal, 40 145-152 evolution, 40 153-154 inhibition, 40 162 kinetic properties, 40 157-162 molecular and spectroscopic properties, 40 125-126... 

In contrast to iron and copper, which dominate the scene of transition metal biochemistry and are components of a variety of metalloproteins, cobalt occupies a relatively modest niche in biology. A biological function of cobalt can only be said to have been established at the molecular level in a few cases involving coninoid coenzymes (7). 

Copper proteins are involved in a variety of biological functions, including electron transport, copper storage and many oxidase activities. A variety of reviews on this topic are available (Sykes, 1985 Chapman, 1991). Several copper proteins are easily identified by their beautiful blue colour and have been labelled blue copper proteins. The blue copper proteins can be divided into two classes, the oxidases (laccase, ascorbate oxidase, ceruloplasmin) and the electron carriers (plastocyanin, stellacyanin, umecyanin, etc.). 

Tt is well known that copper ions are required for the biological function of some enzymes and are detrimental to the function of many others. These effects can often be ascribed to conformational changes. The impact of copper ions on the conformation of nucleic acids is equally dramatic and of potential significance in disturbing the function of the genetic material (1, 2). 

Copper and zinc play Important roles in a wide variety of biological functions. However, their contribution to exercise performance has yet to be evaluated directly. The participation of these elements in muscle activity provides fruitful areas for further exercise physiology research. Detailed reviews of copper metabolism have been written by Underwood (80), O Dell (81), and Li (82). Extensive reviews of zinc metabolism have been provided by Prasad (83), Li (82), Underwood (84), and Sandstead (85). 

The behavior of metals as atoms or ions deeply affects the electrochemical reactions they undergo, and similarly affects the metabolism of plants and animals. Iron, copper, cobalt, potassium, and sodium are examples of metals that are essential to biological function. Some metals such as cadmium, mercury, lead, barium, chromium, and beryllium are highly toxic. 

The biological functions of copper are mostly reflected in the proteins listed in Table 37-5. Like iron, copper is... 

The accompanying table lists the essential elements in the human body. Of special interest are the trace elements, such as iron (Fe), copper (Cu), zinc (Zn), iodine (I), and cobalt (Co), which together make up about one percent of the body s mass. These elements are necessary for biological functions such as growth, transport of oxygen for metabolism, and defense against disease. There is a delicate balance in the amounts of these elements in our bodies. Too much or too little over an extended period of time can lead to serious illness, retardation, or even death. 

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