Molybdenum Cofactor in Humans

Molybdenum is an essential trace element that is crucial for the survival of animals. To date, four molybdenum-dependent enzymes have been identified in humans harboring a molybdenum cofactor in the active center. In humans, sulfite oxidase is the most important molybdenum enzyme catalyzing the terminal step in cysteine catabolism—the oxidation of cytotoxic sulfite into sulfate. A deficiency in the biosynthesis of the molybdenum cofactor results in molybdenum cofactor deficiency and the simultaneous loss of activities of all molybdenum-dependent enzymes, leading to severe neurodegeneration and death in infancy. In this review we first introduce general aspects of all four molybdenum enzymes and describe their deficiencies in humans before we focus on molybdenum cofactor deficiency and discuss different aspects of the disease, including genetic cause and classification of patients, biochemical and clinical presentation, and underlying molecular mechanism. Finally we report recent advances in the treatment of the disease and discuss possible future therapies.