Ceruloplasmin oxidase activity

Blaha K Jr, Havrdova J, Rosina J, et al. 1987. The effect of 110mAg on ceruloplasmin oxidase activity in rats. J Hyg Epidemiol Microbiol Immunol 31 39-43. 

There is a variety of analytical methods used for ceruloplasmin determinations the most frequently used is the p-phenylenediamine oxidase method, by virtue of its high precision. The oxidation rate of p-phenylenediamine or a derivative is measured spectrophotometrically or gasometrically, determining ceruloplasmin oxidase activity. Sunderman and Nomoto (132) determined plasma ceruloplasmin by measuring... 

How much endogenous Fe salts are present in ceruloplasmin solutions and how effective are they as stimulators of ceruloplasmin oxidase activity McDermott et al. 163) have very elegantly demonstrated that Chelex treated solutions of ceruloplasmin were between 1 and 40 nmolar Fe depending on the amount of Fe the solution contained prior to treatment with Chelex (2—20 Fe atoms per... 

The inescable conclusion from these data is that the rate limiting step in ceruloplasmin oxidase activity is independent of the nature of substrate. Indeed, even the small variations in Fmax might be attributed to minute quantities of... 

Increase in blood and urine Mo levels, increases in serum ceruloplasmin, increased xanthine oxidase activity (11) Increased uric acid, decreased copper excretion, high incidence of gout-like disease (11)... 

The blue oxidases contain these three types of copper together The stoichiometry is straightforward with laccase which contains one type-1 and one type-2 copper, and one type-3 dimeric copper site . One would expect two laccase-like sites in ascorbate oxidase and in ceruloplasmin, but the presence of respectively 3 and 1 and 1 and 3 type-1 and type-2 copper atoms has been deduced. Ceruloplasmin shows oxidase activities towards different substrates, like Fe (ferroxidase) and aromatic amines. It plays, moreover, an active role in the transport of copper With the proper precautions against the action of proteinases it can be isolated as a single polypeptide chain... 

The storage role of (Cu,Zn)-SOD in seeds e.g. seems plausible, when the Cu-carrier function of ceruloplasmin is considered The lipophilic anti-inflammatory and anti-ulcer Cu-chelates could also raise the Cu concentration in certain tissues and thus enhance their lysyl oxidase activity. But especially Cu(acetylsalicylate)2 inhibited protine,2-oxoglutarate dioxygenase (EC 1.14.11.2) and lysine,2-oxoglutarate dioxygenase (EC 1.14.1.4), which are also important enzymes in the processing of collagen... 

This blue oxidase, present in the plasma of vertebrates, appears to be multifunctional.905,975 It accounts for some 95% of the circulating copper in a normal mammal, and its concentration fluctuates considerably in diseased states. It appears that ceruloplasmin has a major role in copper transport (as discussed in Section 62.1.11). In addition it has oxidase activity towards three groups of substrates, although its physiological role is not known with certainty. 

In addition, ceruloplasmin shows oxidase activity towards bifunctional aromatic amines and phenols, but with much higher Km values, and also to a group of pseudosubstrates that can rapidly oxidize Fe11. Ceruloplasmin may also have a role as a serum antioxidant. 

The several functions of ceruloplasmin cannot be explained at present. It seems reasonable that this diversity is related to the activity of the copper centres. The general pattern of oxidase activity is probably similar to that of the other blue oxidases, with a type 3 binuclear site serving to bind and reduce dioxygen, with electrons transferred from the type 1 site. The type 2 copper may represent a substrate-binding site. 

Ceruloplasmin Fluman, animal serum Weak oxidase activity 22,66,67... 

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.). 

Ceruloplasmin is an enzyme synthesised in the liver which contains six atoms of copper in its structure. Ceruloplasmin carries 90% of plasma copper the other 10% is carried by albumin. Ceruloplasmin exhibits a copper-dependent oxidase activity, which is associated with possible oxidation of Fe + (ferrous iron) into Fe (ferric iron), therefore assisting in its transport in the plasma in association with transferrin, which can only carry iron in the ferric state. 

Osaki, S., Johnson, D. A., and Frieden, E. (1966). The possible significance of the ferrous oxidase activity of ceruloplasmin in normal human serum./. Biol. Chem. 241, 2746-2751. 

Frieden, E, and Hsieh, H. S. (1976). Ceruloplasmin The copper protein with essential oxidase activity. Adv. ErizymcJ. 44,187-236. 

Ceruloplasmin by p-Phenylenediamine Oxidase Activity, Clin, Chem, Winston-Salem, N,C, (1970) 16,903-910. 

Ceruloplasmin can be assayed immunochemically or functionally (copper oxidase activity). The latter assays measure only native, copper-containing Cp, whereas the former measure both the intact molecule and, to varying degrees, apoCp and proteolytic fi-agments. 

Finally, the effect of a number of anions on the oxidase activity of ceruloplasmin should be mentioned. Holmberg and Laurell (H16) and later Curzon (C18) showed that chloride, acetate, nitrate, bromide, thiocyanate. 

These observations underline the need for meticulous standardization of enz3Tnatic assay techniques for determining ceruloplasmin. With proper standardization, the enzymatic methods are reliable. However, one must always be alert to the possibility that factors other than the concentration of ceruloplasmin may influence the p-phenylenediamine oxidase activity. 

The results of enzymatic determinations of ceruloplasmin are often expressed in arbitrary units, and the values judged in the light of a series of results obtained in normal subjects by the same method. Expression of the enzyme activity in milligrams of ceruloplasmin per unit volume of serum is also possible. The relation between oxidase activity and the amount of ceruloplasmin in serum can be determined by measuring in parallel samples of sera both the oxidase activity and the change of optical density at 610 mix before and after the addition of ascorbic acid or cyanide. On the basis of the known absorbancy index, the ceruloplasmin concentration can be calculated (see Section 2.2.1) and the relation between it and the enzyme activity determined. Alternatively, purified human ceruloplasmin can be used for standardization of the enzymatic method. The ceruloplasmin content of the purified preparation can be determined colorimetrically or, in the case of a highly purified preparation, by nitrogen analysis. Predetermined increments of ceruloplasmin can then be added to aliquots of a selected serum. It is convenient to select a serum with relatively low ceruloplasmin level to start with. Serum of a patient with Wilson s disease, some of whom have no measurable amount of enzyme activity, would be ideal for the purpose however, Walshe (W5) has recently found an inhibitor in these sera. 

Ceruloplasmin is an enzyme exhibiting oxidase activity against several substrates with a pH optimum between 5.4 and 5.9. The best known substrate is p-phenylenediamine or its dimethyl derivative. The oxidase activity is much weaker against other substrates such as hydroquinone, catechol, pyrogallol, DOPA, adrenaline, noradrenaline, serotonin (L4). The physiological substrate of ceruloplasmin, if any, has not yet been found. 

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