Molybdenum Functions

The biological form of molybdenum present in almost all molybdenum-containing enzymes (molybdoenzymes) is an organic molecule known as the molybdenum cofactor. In humans, molybdenum is known to function as a cofactor for three enzymes. Sulfite oxidase catalyzes the transformation of sulfite to sulfate, a reaction that is necessary for the metabolism of sulfur-containing amino acids, such as cysteine. Xanthine oxidase and aldehyde oxidase catalyze hydroxylation reactions involving a number of different molecules with similar structures. Xanthine oxidase catalyzes the breakdown of nucleotides (precursors to DNA and RNA) to form uric acid, which contributes to the antioxidant capacity of the blood. Xanthine oxidase and aldehyde oxidase also play a role in the metabolism of drugs and toxins. Of these three enzymes, only sulfite oxidase is known to be crucial for human health.

Nutrient Interactions

Copper: Excess dietary molybdenum has been found to result in copper deficiency in grazing animals (ruminants). In ruminants, the formation of compounds containing sulfur and molybdenum, known as thiomolybdates, appears to prevent the absorption of copper. This interaction between thiomolybdates and copper does not occur to a significant degree in humans. One early study reported that molybdenum intakes of 500 and 1,500 mcg/day from sorghum increased urinary copper excretion. However, the results of a more recent and well-controlled study of molybdenum intake and copper metabolism in 8 healthy young men indicated that very high dietary molybdenum intakes (up to 1,500 mcg/day) did not adversely affect copper nutritional status.

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