Molybdenum is a chemical element and belongs to the transition metals. In all organisms, it also serves as an essential trace element. Molybdenum deficiency or excess occurs very rarely.
What is molybdenum?
Molybdenum represents a chemical element with atomic number 42. It belongs to the transition metals and is mainly found in minerals. Strained molybdenum is used in metallurgy for the production of alloys. It increases the strength as well as the corrosion and heat resistance of metallurgical materials. Molybdenum occurs mainly in molybdenum glance (MoS2), yellow lead ore (PbMoO4) and powellite Ca (Mo, W)O4. It represents an essential trace element in all organisms. In the molybdenum cofactor it is involved in various enzymatic reactions. Approximately 50 molybdenum-containing enzymes are known in microorganisms. In addition, molybdenum is involved in nitrogen fixation in legumes with the participation of bacteria. At the same time, it may also assist in nitrate reduction for nitrogen uptake in plant organisms. In human and animal organisms, molybdenum-containing enzymes are involved in the metabolism of sulfur-containing amino acids and uric acid. Within the active biomolecules, molybdenum is present as a central atom in a complex with sulfur atoms as ligands. Diseases associated with molybdenum deficiency usually occur only as a result of a hereditary disorder in the synthesis of molybdenum-containing enzymes or in cases of extreme malnutrition.
Function, effects, and roles
Molybdenum plays an extremely important role in the human organism as an essential trace element. It is a component of some enzymes that catalyze vital biochemical reactions in the body. It is involved in the breakdown of sulfur-containing amino acids. Furthermore, it supports the breakdown of purine-containing nitrogen bases, whereby uric acid is formed. It is a cofactor of iron– and flavin-containing enzymes such as xanthine oxidase, aldehyde oxidase and sulfite oxidase. The enzyme xanthine oxidase is responsible for the formation of uric acid from amino acids and nitrogen bases. Aldehyde oxidase catalyzes various metabolic processes in the liver. The bioavailable molybdenum is in the form of the molybdate ion. This ion is incorporated into the molybdenum cofactor. The molybdenum cofactor is a complex compound between molybdopterin and molybdenum oxide. With the help of this factor, the catalytic ability of xanthine oxidase, sulfite oxidase and aldehyde oxidase is established. In addition, molybdenum is also a cofactor for the enzyme NADH dehydrogenase. Molybdenum has also been found to promote the incorporation of fluorine into teeth. Therefore, it can prevent the formation of caries. Furthermore, molybdenum also has bacteriocidal effects, as it inhibits bacteria growth. It is absorbed from food in the form of molybdate ion by the small intestine. The absorption mechanism is believed to be passive. However, little is known about this process. The molybdate ion is immediately bioavailable and binds to molybdopterin under the formation of the molybdenum cofactor.
Formation, occurrence, properties, and optimal values
In the body, molybdenum occurs mainly in bound form. Free molybdate is present in very small amounts. In the blood, it is found primarily in erythrocytes. The largest concentrations of molybdenum are found in the liver, kidneys, adrenal glands and bones. In teeth and bones it is incorporated into apatite crystals. Thereby it has a positive effect on the health of bones and teeth. The excretion of molybdate from the body is mainly through the urine and only in lower concentrations also through the stool. The daily requirement of molybdenum in humans is not precisely known. However, a requirement of 50 to 100 micrograms is assumed. Since the diet contains sufficient molybdenum, a molybdenum deficiency due to malnutrition is very rare. It is present in all foods, but is especially abundant in legumes, wheat germ, many spice plants, eggs, and offal. The established requirement for molybdenum is covered by the diet. However, it is possible that the requirement increases with oxidative stress, chemical exposure, high uric acid levels, disturbed intestinal flora or other intestinal diseases.
Diseases and disorders
Molybdenum deficiency or excess is very rare. When molybdenum is deficient, molybdenum-dependent enzymes cannot function adequately. The breakdown of sulfur-containing amino acids or of purine bases is impaired.Furthermore, the teeth become more susceptible to caries again. The immune system is weakened by the reduction of the protection against oxidative stress. Typical symptoms are heart palpitations, shortness of breath, dysfunction of brain and nerves, agitation or night blindness. In addition, digestive tract disorders, itching, swelling and fluctuating moods may also occur. Existing chronic diseases such as skin infections, mucosal inflammation, or cancer may worsen. Normally, molybdenum intake can be well covered by food. However, there are intestinal absorption disorders that cannot ensure an adequate supply of molybdenum to the body. These include Crohn’s disease, celiac disease or a disturbed intestinal flora. In these cases, however, there is not only a molybdenum deficiency. Other trace elements and vitamins are also inadequately supplied. However, there is also a hereditary disease in which a molybdenum cofactor deficiency occurs. In untreated cases, this disease is fatal. When molybdenum is overdosed by more than 10 to 15 milligrams daily, too much uric acid is produced and gout-like symptoms occur. In addition, it has been found that elevated levels of molybdenum also lead to increased excretion of copper. For this reason, chronic over-supply of molybdenum can lead to copper deficiency with corresponding symptoms. An overdose of molybdenum can also occur in foundry or paint manufacturing workplaces.
