Low Molecular Weight Copper Research Articles

Purification of low molecular weight copper proteins from copper loaded liver

Purification of low molecular weight copper binding proteins from the livers of copper loaded male rats was achieved by sequential ultracentrifugation (186,000g, 2h), ultrafiltration (Amicon PM 30), gel filtration (Sephadex G-75) and anion exchange chromatography (DEAE - Biogel A) of soluble tissue extracts. The three major copper-associated polypeptides obtained which had molecular weights of about 7000, 9,000, and 12,000 daltons contained approximately 2.5g atoms of copper per mole. Amino acid analyses indicated a similarity between these proteins and the copper protein ‘L-6D’ isolated earlier from livers of Wilson's disease patients and distinguished them from metallothioneins which have been isolated from animals administered other trace metal ions.

Activity of a new polyoxime‐copper complex in the reversible uptake of molecular oxygen and carbon monoxide, in the polymerization of acrylonitrile, and in the addition reaction of alcohols to acrolein

AbstractA new polyoxime‐copper complex was prepared from cupric acetate and a polyoxime which is considered to consist largely of 1,2‐bis(hydroxyimino)trimethylene units. The properties of the complex were studied. Its ESR spectrum was found to be similar to that of the low molecular weight copper(II) complex, whose intensity decreases with increasing copper content. The complex shows a catalytic activity in the Michael type addition reaction of alcohols to acrolein, yielding exclusively β‐alkoxypropionaldehyde. In addition, it initiates the polymerization of acrylonitrile under hydrogen pressure (40 to 90 kg/cm2). Furthermore, the complex with a composition ratio Cu: OX ≈ 1:4 (Cu: number of copper atoms, OX: number of hydroxyimino groups in the complex), after being treated with hydrazine hydrate in methanol under nitrogen, can reversibly take up and release ca. 3,2dm3 of molecular oxygen (in water) and 0,8dm3 of carbon monoxide (in methanol) per mole of copper. These activities decrease remarkably with decreasing copper content of the complex.

Superoxide dismutase activity of low molecular weight Cu 2+-chelates studied by pulse radiolysis

The discovery of an accelerated superoxide dismutation [ 1 ] using erythrocuprein led to an overwhelming number of studies on this metalloprotein (for a review see ref. [2] ). The mechanism of this enzymic catalysed reaction was successfully studied by pulse radiolysis [3-51. It was intriguing to realize that erythrocuprein which has apparently evolved [6] to perform so simple a reaction proved, in some ways, far from simple. The situation turned out even more complicated with the knowledge that free Cu2 * catalyses superoxide dismutation in acidic media in a much faster way compared to the reactivity of erythrocuprein under physiological pH conditions [7] . Furthermore, it was demonstrated that low molecular weight copper chelates display marked superoxide dismutase activity at physiological pH values employing the cytochrome c reductase assay [X] . In this context it was of high importance to measure the rate constants for reaction between some of these cupric-peptide chelates and the superoxide ion generated by pulse radiolysis at pH 7 5. The reaction of chelated Cu2 * with superoxide was very fast throughout. The respective second order rate constants of either equivalent of Cu2+ ranged from 0.6 X IO9 M-r see-’ (Cu(ly~)~) up to 1.3 X IO9 M-’

Singlet oxygen decontaminating activity of erythrocuprein (superoxide dismutase)

Erythrocuprein is both a most powerful and specific metalloprotein able to decontaminate highly reactive ′ Δ g singlet oxygen being exclusively generated by K 3CrO 8. Even in concentrations up to 2·10 −10 M erythrocuprein displayed a clearly detectable singlet oxygen decontaminating activity. In contrast to the considerable superoxide dismutase activity of low molecular weight copper chelates (4%) the singlet oxygen decontaminating activity of these model compounds was remarkably low by 4 orders of magnitude compared to the respective activity of native erythrocuprein. From these data it must be concluded that in aerobic biological systems erythrocuprein is acting as a singlet oxygen decontaminating enzyme rather than as a superoxide dismutase. This conclusion was made in the light of the well established specificity of the enzyme and the deleterious action of ubiquitous singlet type oxygen species even in the absence of superoxide.