In this brief the authors explore and review the current knowledge regarding the role of
molybdenum in the evolution of biological systems and their interaction with biogeochemical
cycles. Special emphasis is placed on biological nitrogen fixation and the nitrogen element
cycle. The origin and evolution of molybdenum cofactor biosynthetic pathways as well as the
evolutionary significance of molybdenum containing enzymes appearance is analyzed. Original
data regarding nitrogen fixation pathways and related enzymes molecular evolution processes is
presented. The trace element molybdenum is essential for nearly all organisms and forms the
catalytic center of a large variety of enzymes such as nitrogenase nitrate reductases
sulphite oxidase and xanthine oxidoreductases.
