Enzyme components, copper

The terminal component of the respiratory chain is cytochrome c oxidase, which reduces dioxygen to two molecules of water. This cytochrome was discovered as the Atmungsferment by Warburg already in the 1920s and shown by him to be a heme protein in 1929 [2], an achievement for which he was awarded the Nobel Prize for Physiology or Medicine in 1931. The electron donor of the oxidase, cytochrome c, had been found earlier by Keilin (see [3]), as had one of the oxidase heme components, cytochrome a, whereas Keilin did not observe the dioxygen-reacting cytochrome fl3 until 1939. Keilin had before this discovery maintained that the oxidase is not a heme but a copper enzyme, and we now know that it also contains two... 

Whereas elemental copper adds to the comfort and enjoyment of life, ionic copper is absolutely essential for the maintenance of life. Probably because of copper s relative abundance in the biosphere and the element s ease of undergoing oxidation reduction, organisms have developed enzyme systems that utilize copper in their catalytic action. Copper-containing enzymes have been identified in nearly every type of organism, from the simplest to the most complex, and the chemical reactions catalyzed by these enzymes cover a broad spectrum of metabolic processes (Frieden et al., 1965). Because copper is an integral component of a variety of enzymes, a deficiency of this element or an abnormality in the production of copper enzyme may result in widespread deleterious effects, and often death. In addition, because copper is a very reactive element, an excess of this ion in living cells results in marked changes in metabolism. 

Another problem to be elucidated is the role of copper in cytochrome a. In the known copper enzymes such as tyrosinase and laccase, copper is an important component of the prosthetic group, but is released from the protein moiety by dialysis against potassium cyanide. In the case of cytochrome a, however, the mode of combination of copper must be different, since very little copper is released from the protein moiety by dialysis. The best known method of releasing the copper is by acid treatment. The role of copper in the electron trasnferring system is still obscure, though Cohen and Elvehjem (1934), Yoshikawa (1937), Schultze (1939, 1941), Gallagher et al. (1956), and Gubler et al. (1957) observed, from dietary experiments, that copper-deficient tissues and yeast have a low cytochrome oxidase activity and a decreased content of hemin a. 

Phenylalanine is hydroxylated to tyrosine and then sequentially to 4-hydroxyphenyl-pyruvate and by dioxygenation and rearrangement to 2,5-dihydroxyphenylpyruvate (Figure 3.16) (Arias-Barrau et al. 2004). Hydroxylation involves 6,7-dimethyltetrahydro-biopterin that is converted into the 4a-carbinolamine (Song et al. 1999). Copper is not a component of the active enzyme, although there is some disagreement on whether or not Fe is involved in the reaction for the hydroxylase from Chromobacterium violaceum (Chen and Frey 1998). 

This short section attempts to bring together the range of metalloenzymes that are encountered in biodegradation and biotransformation. Fe is the most common component of enzymes, and is followed in freqnency by zinc and molybdennm, while some important enzymes contain nickel, copper, manganese, tnngsten, or vanadinm. 

Copper is a component of several enzymes that have quite different catalytic properties ... 

In addition to all of the expected enzyme systems present in leaf tissue, fresh tea leaves contain a high level of polyphenol oxidase that catalyzes the oxidation of the catechins by atmospheric oxygen. Tea polyphenol oxidase exists as series of copper-containing (0.32%) isoenzymes. The major component has a molecular weight of about 144,000.54 The enzyme is concentrated in the leaf epidermis.55 Soil copper deficiency is sometimes responsible for inadequate oxidation during processing.56... 

Bluish, shimmering, brittle, relatively reactive metal. Is guite guickly covered with a protective oxide layer, which is why iron is treated with zinc With copper, forms the popular alloy brass, which was already known in antiquity. Used in batteries and as a stabilizer in plastics. Zinc oxide is used as a white pigment Zinc ions are essential to all life forms, e.g., as a component of alcohol dehydrogenase and many other enzymes. Hence human beings (70 kg) carry about 2.3 g (half as much as iron). 

Copper is an essential micronutrient required in the growth of both plants and animals. In humans, it helps in the production of blood haemoglobin. In plants, copper is an important component of proteins found in the enzymes that regulate the rate of many biochemical reactions in plants. Plants would not grow without the presence of these specific enzymes. Research projects show that copper promotes seed production and formation, plays an essential role in chlorophyll formation and is essential for proper enzyme activity, disease resistance and regulation of water in plants (Rehm and Schmitt, 2002). 

Copper Liver and organ meats grains, legumes, nuts, seeds (esp. cocoa powder) Component of many enzymes, especially oxidases Amine oxidases Lysyl oxidases Cytochrome oxidase... 

Copper is a component of many enzymes including amine oxidase, lysyl oxidase, ferroxidase, cytochrome oxidase, dopamine P-hydroxylase, superoxide dismutase and tyrosinase. This latter enzyme is present in melanocytes and is important in formation of melanin controlling the colour of skin, hair and eyes. Deficiency of tyrosinase in skin leads to albinism. Cu " ion plays an important role in collagen formation. 

The cytochrome o from Azotobacter vinelandii is reported to consist of one polypeptide of molecular weight 28 000 with two identical heme components. It has also been isolated from the thermophile PS3,1319 Escherichia coli, Vitreoscilla, Pseudomonas aeruginosa, and Rhodopseudomonas spp. The enzyme from Vitreoscilla consists of two identical polypeptides of molecular weight 13 000 and two moles of protoheme IX. A cytochrome b562-o complex from E. coli contains two peptides and, strangely, copper.1320... 

The role of the transition elements in living systems is equally important. Iron is present in biomolecules such as hemoglobin, which transports oxygen from our lungs to other parts of the body. Cobalt is an essential component of vitamin B12. Nickel, copper, and zinc are vital constituents of many enzymes, the large protein molecules that catalyze biochemical reactions. 

Copper Component of enzymes in iron metabolism Men women 900 pg/d... 

Together with A. DiSpirito of Iowa State University, we conducted in 2007 a Mossbauer study of pMMO from M. capsulatus (Bath), aimed at determining whether the (quite active) preparations contained iron components assignable to a catalytically active site.44 Before we discuss the Mossbauer spectra, a comment about MMO catalytic activity will be in order. Biochemists have developed a propylene oxidation assay, and the MMO activity is measured in units of nmol propylene oxide/min/mg protein.45 The activities of pMMO samples investigated by us had 1500 units in whole cells, 500 units in membrane fractions (with the enzyme residing still in the membrane), and 160 units for the purified enzyme. Preparations from laboratories favoring a copper catalytic site have <20 units or no activ-ity.33,34,38 39 46 47 The above values show that catalytic activity is lost in the course of the preparation, either by loss of metals from the active site or by conformational changes not yet appreciated. 

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