Differential Reduction of CO2 by Molybdenum and Vanadium Nitrogenases

The molybdenum and vanadium nitrogenases are two homologous enzymes with distinct structural and catalytic features. Previously, it was demonstrated that the Vnitrogenase was nearly 700 times more active than its Mo counterpart in reducing CO to hydrocarbons. Herein, a similar discrepancy between the two nitrogenases in the reduction of CO2 is reported, with the Vnitrogenase being capable of reducing CO2 to CO, CD4, C2D4, and C2D6, and its Mocounterpart only capable of reducing CO2 to CO. Furthermore, it is shown that the Vnitrogenase may direct the formation of CD4 in part via CO2-derived CO, but that it does not catalyze the formation of C2D4 and C2D6 along this route. The exciting observation of a Vnitrogenase-catalyzed CC coupling with CO2 as the origin of the building blocks adds another interesting reaction to the catalytic repertoire of this unique enzyme system. The differential activities of the V and Monitrogenases in CO2 reduction provide an important framework for systematic investigations of this reaction in the future.