Role of Metals in Biochemistry

Metals in biological systems like humans are used for very diverse purposes [9]  

The function of metals in a biological system can only be appreciated in terms of the compartments into which these elements are placed by the use of metabolic energy. Some elements are moved around as simple ions (Na, K ) others in protein complexes (many trace metals). Different elements are concentrated in different compartments ([9,10] (see Table 1). The concentrations of Na+, K+, Mg +, and Ca are controlled by membranes and the position of pumps and channels in the membranes. By contrast trace metals, e.g., Cu and Zn, are bound to proteins so that their location is also controlled by the binding to filamentous structures. 

In humans the main cations acting as electrolytes are Na , K, Ca , and Mg [10,11]. The main task of Na is to maintain osmolality. By this it is closely correlated with the regulation of the extracellular volume and the water balance. The main functions of K are osmoregulation and maintainance of the membrane resting potential. Ca is a trigger for many enzymes. About 90% 

More than 300 reactions are catalyzed by zinc-containing enzymes [82]. Zinc can be found with insulin, in the reproductive tract, in the DNA-binding proteins, and in oxidoreductases, transferases, lyases, isomerases, and ligases. 

Copper is the preferred redox catalyst in an oxidizing medium. It is the prosthetic element of a significant number of specific proteins [10,12], Copper-containing enzymes are cytochrome-c-oxidase, monoaminooxidase, and superoxide dismutase. In serum/plasma 90-95% of copper is bound to a specific transport protein, ceruloplasmin. 

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Wetterhahn-Jennette K (1981) The role of metals in carcinogenesis biochemistry and metabolism. Environ Health Perspect 40 233-252... 

Oxidative dehydrogenation reactions of alcohols and amines are widespread in enzymatic biochemistry, and are of potential importance with regard to the operation of fuel cells based on simple alcohols such as methanol. The nature of products, and their rates of formation, may vary depending on the reaction conditions, and a role of metal ions has been recognized. The oxidation of amines may lead to a variety of products (nitriles, nitro species, etc.) although dehydrogenated diimine products are obtained quantitatively when the oxidation of the amine occurs via coordination to metal centers. A review is available on the mechanisms of oxidative dehydrogenations of coordinated amines and alcohols (93). 

Garner, C.W.J., and F.J. Behai. 1974. Human liver aminopeptidase. Role of metal ions in mechanism of action. Biochemistry 13 3227. 

In recent years, more emphasis has been placed on compounds with metal-metal bonds (especially the cluster compounds) and on the mechanism of reactions. The observed role of transition metals in biochemistry and many industrial processes as catalysts 51, 65) has also abetted research on them. The literature on these compounds has indeed become quite substantial it has recently been compiled by Bruce 34, 35). 

The chemistry and biochemistry of Hpx has been reviewed and a crystal structure is available. Hemopexin is present in serum at about 10 pM and its primary function is to transport released heme to its degradation site in the parenchymal cells of the liver via receptor-mediated endocytosis. Encapsulation of a single heme by Hpx occurs via bis-histidyl protein side-chain coordination of the Fe. Spectroelectrochemical investigation of the heme-Hpx assembly gives insight into the role of Hpx in controlling the reduction potential of the heme Fe, the efficiency of electron transfer at the metal centre, the influence of bis-histidyl coordination at the Fe centre, and the possible role of Fe redox in the Hpx-mediated transport and recycling of heme. 

In this article we propose to survey the role of iron as a conformational determinant in polypeptides and in non-haem proteins. This aspect of iron coordination research has been either ignored or only sporadically dealt with in reviews concerned with metalloproteins. By stressing this often circumstantial aspect of iron biochemistry it is our hope that the relevance of metals in general as fundamental structural factors in biomolecules will be brought into proper perspective. 

Source Adapted from A.L. Feig and O.C. Uhlenbeckv. The Role of Metal Ions in RNA Biochemistry, in The RNA World. 2nd edition, 287-319 (New York Cold Spring Harbor Laboratory Press, 1999). ... 

Myers C, Gianni L, Zweier J, Muindi J, Sinha BK, Eliot H (1986) Role of iron in adriamycin biochemistry. Fed Proc 45 2792-2797 Naganuma A, Satoh M, Koyama Y, Imura N (1985) Protective effect of metallothionein inducing metals on lethal toxicity of cis-diamminedichloroplatinum in mice. Toxicol Lett 24 203-207... 

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