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The Grolier Encyclopedia had this info under the copper entry: Copper is a trace element essential to the healthy life of many plants and animals, in which it usually occurs as part of the oxidizing enzymes such as ascorbic acid oxidase, tyrosinase, lactase, and monoamine oxidase. These enzymes, which are high-molecular-weight proteins containing 0.05%-0.35% of Cu, play an important part in living oxidation and reduction reactions, in which the copper undergoes cyclic changes between Cu(I) and Cu(II) oxidation states. The metal is tightly bound to ligand sites, containing oxygen, sulfur, or nitrogen atoms on the protein. The normal diet of humans includes between 2 and 5 mg of copper per day, exceeding the body maintenance requirements of about 2 mg per day. The hereditary deficiency of the protein ceruloplasmin, known as Wilson's disease, is associated with a pathological increase in the copper content of almost all tissues, particularly the brain and liver. Albino mammals lack the normal form of the copper-containing enzyme tyrosinase, which participates in the synthesis of the pigment melanin. Copper can be toxic in large quantities, especially to lower organisms such as bacilli, fungi, and algae. Ron <[log in to unmask]> Ronald F. Vetter