Molybdenum is an essential trace element that is naturally present in many foods and is also available as a dietary supplement. Molybdenum is a structural constituent of molybdopterin, a cofactor synthesized by the body and required for the function of four enzymes: sulfite oxidase, xanthine oxidase, aldehyde oxidase, and mitochondrial amidoxime reducing component (mARC). These enzymes metabolize sulfur-containing amino acids and heterocyclic compounds including purines and pyrimidines. Xanthine oxidase, aldehyde oxidase, and (mARC) are also involved in metabolizing drugs and toxins.