Copper is a chemical element and is one of the transition metals. In biological organisms, it occurs as a trace element. There it fulfills important functions as a cofactor in metalloenzymes.
What is copper?
Copper represents an important trace element in all biological organisms. It is a component of important enzymes as a cofactor. In nature, copper often occurs as copper ore together with iron or alone as copper sulfide. In its native state, it is a heavy metal with low reactivity. It belongs to the group of semi-precious metals. As a pure metal, copper has a light red color. On the surface, a corrosion layer slowly develops, changing from a reddish-brown color to a bluish green. Within organisms it has different meanings. For many bacteria, copper represents a poison because it can form complexes with thiol groups of proteins. It also reacts with the lipids of cell membranes to form peroxides and is thus responsible for the formation of free radicals. However, it also supports many enzymes in vital reactions. In this context, iron and copper metabolism are closely linked. Copper deficiency diseases occur very rarely because the copper requirement can be well covered by the diet. More serious effects are caused by excessive copper concentrations in the body. Hereditary copper metabolism disorders represent Wilson’s disease and Menkes syndrome.
Function, effects, and roles
Copper has great importance in the human organism as a trace element. In this context, it promotes the function of many metalloenzymes as a cofactor. Copper is mainly bound to the transport protein coeruloplasmin. Coeruloplasmin is responsible for oxygen utilization and electron transport. It performs both transport and enzyme functions. The enzyme plays an important role in iron metabolism. It oxidizes divalent iron bound to ferritin to trivalent iron, which can bind to transferritin. The iron is thus transferred from the storage form to the transport form and is available for oxygen transport. In order to perform this function, coeruloplasmin requires copper as a cofactor. Coeruloplasmin is also able to oxidize the aromatic diamines norepinephrine, melatonin and serotonin. In addition to mobilizing iron, copper, in conjunction with enzymes, is also co-responsible for the formation of the nerve-enveloping myelin layer, protein metabolism, cell growth and the synthesis of melamine. It is absorbed from food in the intestine, stored in the liver, bound from there to coeruloplasmin or excreted again via the bile. The liver stores about 10 to 15 milligrams of copper. Furthermore, copper is an essential component of monoaminooxidase or cytochrome oxidase. Monoaminooxidase catalyzes the breakdown of monoamines such as norepinephrine, epinephrine or dopamine. Cytochrome oxidase is responsible for the mitochondrial respiratory chain.
Formation, occurrence, properties, and optimal levels
The human organism depends on the dietary intake of copper. It is mainly found in cereals, liver, vegetables, nuts or even chocolate. However, copper is also present in the other foods. The daily copper intake of humans is about 2.5 milligrams. Of this, 0.5 to 2 milligrams are absorbed. The liver continues to store 10 to 15 milligrams of copper. The blood copper level in an adult is about 74 to 131 micrograms per deciliter. Up to 60 micrograms of copper are excreted daily through the urine. Copper deficiency is very unlikely because of its low requirement and daily availability.
Diseases and disorders
Serious diseases can occur in connection with copper. At the same time, copper deficiency is very rare. Most often, there is an excess. In high concentrations, copper has a toxic effect. First, however, we will discuss possible deficiency conditions. A copper deficiency due to an incorrect diet is virtually impossible. It is sufficiently present in the diet and the requirement is also not very high. However, an increased intake of zinc or molybdenum can increase copper excretion, resulting in an increased requirement. The main cause of copper deficiency, however, is malabsorption. This can be caused by serious intestinal diseases such as celiac disease, Crohn’s disease or ulcerative colitis.Typical deficiency symptoms manifest themselves in anemia, weakening of the immune system, disorders of the nervous system, pigmentation disorders of the skin, osteoporosis or connective tissue weakness. However, in addition to copper deficiency, there is also a general lack of nutrients, trace elements, minerals or vitamins. An isolated copper deficiency is at most to be expected with a prolonged intake of zinc supplements or prolonged artificial nutrition. Much more serious is an overdose of copper. Actually copper represents a body poison. In case of an over-supply, free copper also accumulates, which immediately forms free radicals. This leads to cell damage. Up to 5 milligrams of copper per day are harmless. However, if the intake rises above this level, poisoning can occur. Copper-containing containers in which acidic beverages or foods have been stored for a long time slowly dissolve and release copper into the food. This can also cause poisoning. Copper poisonings manifest as abdominal cramps, vomiting and diarrhea. Sometimes they are fatal. In most cases, the excess copper is excreted again. However, there are two hereditary diseases of copper metabolism. These are Wilson’s disease and Menkes syndrome. Wilson’s disease is a copper storage disease. The excretion of copper via the bile is disturbed. The copper accumulates in the liver and eventually leads to liver cirrhosis. In Menkes syndrome, the absorption of copper through the intestine is impaired.
