Ceruloplasmin molecular weight

Contrary to popular belief, ceruloplasmin5, the principal copper-containing protein in plasma, ceruloplasmin, is not involved in copper transport. This is clearly underlined by the clinical observation that patients with aceruloplasminaemia (i.e. lacking ceruloplasmin in their blood) have perfectly normal copper metabolism and homeostasis. Copper is transported in plasma mostly by serum albumin with smaller amounts bound to low-molecular weight ligands like histidine. Likewise zinc is mostly transported in plasma bound to proteins (albumin and ot2-macroglobulin). 

Ceruloplasmin is the major copper-containing protein in mammalian blood plasma (see Section 62.1.8.5), and appears to consist of a single polypeptide chain of molecular weight 130 000.1341 The nine-line superhyperfine splitting in the ESR spectrum of the type 2 copper has been interpreted in terms of four equivalent nitrogen ligands.978... 

There is some evidence that localized copper imbalance is related to rheumatoid arthritis (RA) conditions. Low molecular weight copper complex concentrations in plasma and synovial fluids are increased as part of the body s natural response to RA. Secondly, when such increases are induced by copper administration, they have a powerful antiinflammatory effect. More data are required to show the medical significance of these changes. Three parameters which should be reported are (i) total copper levels (by atomic absorption spectrophotometry) (ii) total ceruloplasmin levels (by autoimmune assay) and (iii) the relative molecular weight distribution (by Sephadex gel filtration and ultrafiltration). 

Sugawara N, Sugawara C. 1984. Effect of silver on ceruloplasmin synthesis in relation to low-molecular-weight protein. Toxicology Letters 20 99-104. 

Ceruloplasmin seems not absolutely necessary for life, as several people have been found to lack this protein. However, these people suffer froni diabetes and retinal degeneration, and iron deposits occur in their brain, liver, and pancreas (I larris, 1995). The exact physiological role of ceruloplasmin remains unclear, but it is related somehow to the transfer of iron in and out of ferritin. Ferritin is a huge multisubunit iron storage protein with an overall molecular weight of 450 kDa. It can hold up to 2500 iron atoms. Studies have shown that iron can spontaneously be inasrporated into ferritin, and also that ceruloplasmin can load iron into ferritin. 

The metal-binding proteins metallothionein and ceruloplasmin are recurring themes in the study of zinc and copper. Metallothionein is a small protein with a protein binds zinc and copper ions, as well as nonnutritive heavy metals. The protein consists of about 60 amino acids, and has a molecular weight of about 7000. One third of these amino acids (20 of them) are cysteine. The 20 sulfhydryl groups of these cysteine residues can bind a total of 7 bivalent metal ions, i.e., 7 zinc atoms or 7 copper atoms (Kagi and Schaffer, 1988). 

Ceruloplasmin, the copper protein in plasma, deserves special attention. Human plasma contains approximately 32 mg/100 ml of this protein (see Table 6) (C2, C12, R4). According to the recent careful measurements of Kasper and Deutsch (K3), the molecular weight of ceruloplasmin is 160,000, somewhat higher than the 151,000 obtained by Pedersen (P3). Ceruloplasmin is an a2-globulin and contains 8 atoms of copper per molecule (H14). In addition to being a metalloprotein, it is a glycoprotein containing 7% carbohydrate hexose, hexosamine, and neuraminic acid (L4). Ceruloplasmin has been prepared in a pure form from human and pig sera (H14). Several newer methods are now available for its isolation and purification (B29, C20, D4, L4, S4, S7, S39). 

When conventional enzymatic assays are used to determine SOD activities in tissues, however, nonspecific reactions due to other proteins or low-molecular-weight compounds possessing SOD-like activities in the tissues can cause erroneous results. For example, serum ceruloplasmin reacts stoichiometrically with 02, though the reaction is noncatalytic under physiological conditions (B2,G10, HI,VI). Immunochemical assays for SODs are more reliable because the molecular weights and subunit structures of Cu,Zn-SOD and Mn-SOD are quite different from each other, and immunochemically these proteins do not cross-react. 

Glycoproteins substances of high molecular weight having many of the physical properties of a protein, but containing covalently bonded carbohydrate component s) mucoproteins, mucosubstances, mucins ovalbumin, thyroglobulin, ceruloplasmin... 

In between the lines of haptoglobin and a2-macroglobulin, the light line caused by ceruloplasmin is just visible (U2). It is the principal carrier of copper, 8 atoms per molecule besides, it contains 9.5 % of hexoses and has a molecular weight of 150,000 (S9). Its polyphenol-oxidase activity can be used for localization and, coupled with ImEl, for identification. 

A remarkable increase in SOD-mimetic activity was found in a comparison of synovial fluid from rheumatoid arthritis and osteoarthritic patients with normal control values [613]. The increase in SOD-mimetic activity correlated with increased rheumatoid disease activity and increasing progression of disease severity. There was also a good correlation between SOD-mimetic activity and C-reactive protein in synovial fluid from patients with rheumatoid arthritis. This SOD-mimetic activity may be attributed to either an elaboration of ceruloplasmin by synovial cells [614] or the liver along with copper albumin and amino-acid copper complexes which, in part, accounts for the established increase in synovial fluid copper and ceruloplasmin in rheumatoid arthritis [30] and it is well known that ceruloplasmin [102, 489, 615] as well as amino-acid and other small-molecular-weight copper complexes have SOD-mimetic activity [287-295, 327]. 

Ceruloplasmin (Cp) is the blue copper protein first reported in the plasma of most vertebrates by Holmberg and Laurell in 1948 (il). In normal circumstances, it accounts for over 98% of the copper in the plasma. Cp has a molecular weight of 160,000 with 7 Cu/mole. Some of the other vital statistics of this serum protein are included in Table II. A recent extensive summary of the chemical properties of Cp has been published by Jamison (12),... 

Freeman and Daniel 226) one of 124,000 both being based on sedimentation-equilibrium studies, and in addition, the amino acid and carbohydrate composition suggest a molecular weight near 130,000 119). These studies appear to establish the molecular weight of ceruloplasmin to be near 124,000—134,000. Morell et al. 134) have carefully determined the Cu content and dry weight of the protein finding a value of 0.275 0.009%, w/w Cu which for a molecular weight of... 

Copper Proteins — Systems Containing the Blue Copper Center Table 4. Molecular weight and copper determinations of ceruloplasmin... 

Ceruloplasmin. This is the most well-known and yet the least understood copper protein. It is an a2-globulin and there is conclusive evidence that this 132000 molecular weight glycoprotein has just one polypeptide chain [9]. It has 7% carbohydrate. It contains six atoms of copper per molecule. Copper in ceruloplasmin exists in both cupric and cuprous forms. Partial removal of copper from ceruloplasmin results in the loss of its characteristic blue color and loss of enzymatic activity. Ceruloplasmin has enzymatic oxidase activity toward several substrates at pH 5.4-S.9. The best substrate is p-phenylenediamine or its dimethyl derivative. Ceruloplasmin can oxidize ferrous ion to ferric ion. The ceruloplasmin level in the newborn is less than 10 mg/100 mL serum. It rises to adult levels (30.4 5 mg/lOO mL) by 2-4 months of age and continues to rise to a peak at 2-3 years and this declines to adult levels by 12 years of age. The level of ceruloplasmin is affected by various pathological states. Usually, a pronounced deficiency of this protein in serum is characteristic of both Wilson s and Menkes s diseases although normal levels have also been reported in the case of Wilson s disease. 

Copper values are so well established that a recent report has listed the distribution of the element among the components of human plasma or serum [30]. According to this analysis, copper in normal adult plasma exists at an average of 0.600 (xg/mL associated with ceruloplasmin, 0.12 (jig/mL with transcuprein, 0.150 p,g/mL with albumin, and 0.090 p,g/mL with the low molecular weight components (<30,000). Such profiling of trace elements will be very meaningful in clinical diagnosis and treatment. 

Serum from patients with rheumatoid disease has been shown to contain increased concentrations of ceruloplasmin and low molecular weight Cu complexes. Since these increases occur prior to remission and low molecular weight Cu complexes are known to have anti-inflammatory activity, it is suggested that the increase in serum Cu containing components is a physiological response to these diseases. This physiological response then facilitates biological processes required to prevent further tissue destruction and promote tissue repair which leads to remission. 

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