The isolated iron-molybdenum cofactor of nitrogenase catalyses hydrogen evolution at high potential

The isolated cofactor of nitrogenase FeMoco catalyses hydrogen evolution at the high potential associated with the FeMoco(ox/semi-red) couple(E degree s = -280 mV vs. NHE, C6F5S- ligated form); analysis of the current-potentia l dependence of the catalysis suggests a mechanism involving rate-determini ng loss of H-2 from an FeMoco(H)(2)(red) intermediate (k = 3 s(-1)); the re latively slow kinetics of this step may be related to an obligatory role fo r hydridic intermediates in substrate reductions by nitrogenase.