Molybdenum

What Is Molybdenum?

Molybdenum is an essential trace mineral required in very small amounts. An adult body contains only 9-16 mg of molybdenum, primarily in the liver, kidney, adrenal glands, and bone. It is unique among essential trace minerals in that it functions as the catalytic center of a special cofactor — the molybdenum cofactor (MoCo) — rather than being bound directly to enzymes as a free ion. The molybdenum cofactor is synthesized in cells and is then incorporated into molybdoenzymes that catalyze specific oxidation-reduction reactions.

Key Functions

Molybdenum's biological roles are mediated through four known human molybdoenzymes:

• Xanthine oxidase/dehydrogenase: Catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid, the final steps in purine catabolism. Gout results from hyperuricemia, in which uric acid crystals deposit in joints.
• Aldehyde oxidase: Oxidizes various aldehydes, including those derived from alcohol metabolism, and participates in drug and xenobiotic metabolism in the liver.
• Sulfite oxidase: The most clinically important molybdoenzyme in humans — it catalyzes the oxidation of sulfite to sulfate, the final step in the metabolism of sulfur-containing amino acids (cysteine, methionine, taurine). Inherited deficiency of sulfite oxidase is a rare but devastating condition causing severe neurological damage, seizures, and early death.
• Mitochondrial amidoxime reducing component (mARC): A recently characterized enzyme that reduces N-hydroxylated compounds and participates in drug metabolism.

Dietary Reference Values and Food Sources

The RDA for molybdenum is 45 mcg/day for adults. The UL is 2,000 mcg/day. Molybdenum is abundant in legumes, grains, and nuts, and most people easily exceed the RDA through normal eating. Soil content influences plant molybdenum levels. Rich food sources include:

• Beef liver (3 oz): ~138 mcg
• Black-eyed peas, cooked (1 cup): ~181 mcg
• Lima beans, cooked (1 cup): ~104 mcg
• Yogurt, plain (1 cup): ~26 mcg
• Oats, cooked (1 cup): ~15 mcg

Deficiency and Toxicity

Dietary molybdenum deficiency is extraordinarily rare because the requirement is so low and the mineral is so widely distributed in food. The only documented cases of acquired deficiency occurred in patients on long-term total parenteral nutrition (TPN) without molybdenum supplementation, presenting as elevated blood methionine, decreased uric acid, and neurological problems. Genetic molybdenum cofactor deficiency is a rare autosomal recessive inborn error of metabolism. High molybdenum intake (above approximately 10-15 mg/day from heavily contaminated food or water) has been associated with gout-like symptoms due to elevated uric acid production.