Ceruloplasmin characterization

Oehme FW (1978) Mechanisms of heavy metal inorganic toxicides. In Oehme (ed) Toxicity of heavy metals in the environment. Dekker, New York, pp 69-85 Orion Research Inc (1970) Mercury by electrode. Orion Newslett 11 41-42 Ortiz DF, Kreppel L, Speiser DM, Scheel G, McDonald G, Ow DW (1992) Heavy metal tolerance in the fission yeast requires an ATP-binding cassette-type vacuolar membrane transporter. EMBO J 11 3491-3499 Percival SS, Harris ED (1990) Copper transport ceruloplasmin characterization of the cellular uptake mechanism. Am J Physiol 258 C140-C146 Philipson KD (1985) Sodium-caldum exchange in plasma membrane vesicles. Annu Rev Physiol 47 561-571... 

Copper oxidases are widely distributed in nature, and enzymes from plants, microbes, and mammals have been characterized (104,105). The blue copper oxidases, which include laccases, ascorbate oxidases, and ceruloplasmin, are of particular interest in alkaloid transformations. The principle differences in specificity of these copper oxidases are due to the protein structures as well as to the distribution and environment of copper(II) ions within the enzymes (106). While an in vivo role in metabolism of alkaloids has not been established for these enzymes, copper oxidases have been used in vitro for various alkaloid transformations. 

Studies of other sources of ceruloplasmin may eventually prove useful in structure elucidation, but have already clarified some of the copper chemistry. Ceruloplasmin from goose serum has been isolated, purified, and characterized. This ceruloplasmin has less carbohydrate attached, but two forms may be isolated under some conditions. It is clear that these are not products of proteolytic degradation, but perhaps they might have a different carbohydrate attached. The two type I sites have higher extinction coefficients than type I sites in other ceruloplasmins, reflecting a modestly different environment (Hilewicz-Grabska et al, 1988). 

As demonstrated with "Cu in rats, (Cu,Zn)-SOD receives its copper from ceruloplasmin after 2-3 days The (Cu,Zn)-SOD activity in erythrocytes is reduced in Cu deficiency, as shown with several species With rats e.g. during Cu depletion, plasma Cu and ceruloplasmin were decreased by 78 and 75% respectively against 72 % and only 56 % for the blood cell Cu and (Cu,Zn)-SOD respectively In three patients with Wilson s disease the SOD level of erythrocytes was normal, although the disease is characterized by an accumulation of Cu in the liver e.g. and usually by low concentrations and sometimes the absence of ceruloplasmin... 

The oxidation of dopamine by ceruloplasmin yielded a free radical with a very short lifetime, characterized by an EPR signal at g = 2.006 Dimethyl-p-phenylenediamine was oxidized faster by the enzyme to the free radical Wurster s red, which was further oxidized by the enzyme in another one-electron step. The free radical seemed, moreover, to be stabilized by ceruloplasmin... 

Cartwright and Wintrobe and their co-workers suggested a link between copper deficiency and anemia in mammals 50 years ago (see Lahey et al., 1952). Cartwright subsequently demonstrated that this copper-dependent anemia was unresponsive to iron supplementation but was corrected on administration of ceruloplasmin (see Lee et al., 1968). The molecular basis of this link was indicated by Osaki and Friedan, who characterized the ferroxidase activity of ceruloplasmin and kinetically demonstrated that Cp could play a critical role in catalyzing trafficking of the potentially cytotoxic Fe(II) in the plasma to apoA f (see Frieden and... 

Based on present sequence data, known or likely ferroxidase enzymes can be identihed in several eukaryotes. These enzymes are listed in Table 11. All are multicopper oxidases, by sequence homology at least. In mammals, they include ceruloplasmin and, most likely, hephaestin (Hp), although only mouse Hp (mHp) has been characterized at this time (Vulpe et al., 1999). The alignments in Fig. 5A show that mHp is essentially... 

Catalytic reaction schemes for laccase and ceruloplasmin have been formulated on the basis of the mechanistic studies and the state of characterization of the copper redox centers at this time. They are outlined in the reviews on laccase by Reinhammar (10) and on ceruloplasmin by Ryden (26). The degree of correctness of these reaction schemes is rather limited due to the fact that the structure and spatial arrangement of the copper centers were unknown at this time. 

The disease is a rare inherited disorder characterized by a progressive degeneration of the lenticular nucleus in the brain and by cirrhosis of the liver. Barbeau et al. (Bl) studied a case of Wilson s disease which presented normal ceruloplasmin and serum copper values but increased excretion of kynurenine, 3-hydroxykynurenine, and conjugated anthra-nilic acid in xurine after an oral dose of 2 g L-tryptophan. This defect in tryptophan metabolism could be related to that of other amino acids and to the actual content of ceruloplasmin in Wilson s disease (Bl). These findings corroborated Marver s (M2) investigations demonstrating a definite excretion of kynurenine and 3-hydroxykynurenine in abnormal proportions after a tryptophan load in a case of Wilson s disease. 

Some copper compounds have been used therapeutically in the past. Small quantities of copper salts enhance the physiological utilization of iron and are thus often present in hemopoietic formulations. Copper chloride and copper sulfate are used in parenteral nutrition solutions. The artificial radioactive copper isotope Cu has been used in mineral metabolic studies. Excess accumulation of copper can occur due to an abnormality of ceruloplasmin and causes Wilson s disease and Menkes disease, which are both characterized by copper accumulation (SEDA-22, 244) (9). 

Yang F, Naylor SL, Lum JB, Cutshaw S, McCombs JL, Naberhaus KH, et al. Characterization, mapping, and expression of the human ceruloplasmin gene, Proc Natl Acad Sci USA 1986 83 3257-61. 

Iron Metabolism. Copper-containing enzymes— namely ferroxidase I (ceruloplasmin) and ferroxidase II, and the recently described hephaestin in the enterocyte—oxidize ferrous iron to ferric iron. This allows incorporation of Fe into transferrin and eventually into hemoglobin. Ferroxidase II is a yellow protein, the importance of which in iron metabolism is not as well characterized as that of ceruloplasmin. 

Wilson s disease is an autosomal recessive disease of copper metabolism. It has a prevalence of 1 in 30,000 live births in most populations. The disease has a highly variable clinical presentation. It is characterized by impairment of biliary copper excretion, decreased incorporation of copper into ceruloplasmin, and accumulation of copper in the liver and, eventually, in the brain and other tissues. The biochemical findings include low serum ceruloplasmin, high urinary copper excretion, and high hepatic copper content. Some patients have normal serum cerulo-plasmia levels, and heterozygous individuals do not consistently show reduced levels of this protein. 

Aceruloplasminemia is an autosomal recessive disorder characterized by progressive neurodegeneration and accumulation of iron in the affected parenchymal tissues. Iron accumulation in this disorder is consistent with ceruloplasmin s role as a ferroxidase in iron metabolism (discussed in Chapter 29). 

B28. Broman, L., Separation and characterization of two ceruloplasmins from human serum. Nature 182, 1655-1657 (1958). 

Laccase, ascorbate oxidase, and ceruloplasmin are the classical members of the multicopper oxidase family also known as blue oxidases. Recently, a small number of bacterial members of this family have been characterized, including CueO from E. coli a spore-coat laccase (CotA) from Bacillus suhtilis and phenoxazinone synthase from Streptomyces antibioticus The catalyzed reaction of these enzymes except for phenoxazinone synthase is given in Equation (11). A comprehensive overview of the broad and active research on blue copper oxidases is presented in Messerschmidt. Recent results have been included in a review on the reduction of dioxygen by copper-containing enzymes. The nature and number of the different copper sites in blue oxidases has been described in the sections about the type-1 copper site and the trinuclear copper cluster. 

The blue multicopper oxidases constitute a heterogeneous family of enzymes from different sources (7). In addition to the well characterized members of this family, ascorbate oxidase (45,46), laccase (47,48), and ceruloplasmin (49,50), all from higher organisms, two other proteins have attracted much recent interest FetSp, which is involved in iron uptake in yeast (51), and CueO, which is required for copper homeostasis in Escherichia coli (52). The characteristic reactivity of these enzymes is the one-electron oxidation of four substrate equivalents coupled to the four-electron reduction of dioxygen to water (1). These processes occur at a catalytic unit constituted by four copper atoms classified according to their spectroscopic properties in... 

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