Molybdenum Cofactors and Their Role in the Evolution of Metabolic Pathways

Molybdenum (Mo) is essential for (nearly) all biological systems, both Eukaryotes and Prokaryotes. Molybdenum, indeed, bounds to a pterin and forms the molybdenum cofactor (Mo-co) that, in different variants, represents the active compound at the catalytic site of all molybdenum-containing enzymes in nature. In some microorganisms, tungsten (W) is also coordinated by pyranopterin (W-co). The exchangeable use of these two elements probably traces its origin very far into the past.