The kinetics of the reduction of isocyanides, acetylenes and the cyanide ion by nitrogenase preparation from Azotobacter chroococcum and the effects of inhibitors.

1. Nitrogen-fixing preparations from Azotobacter chroococcum reduced substrates with the following K(m) values: methyl isocyanide, 1.8x10(-4)m; ethyl isocyanide, 2.5x10(-2)m; cyanide ion, 1.4x10(-3)m; acetylene, 1.2x10(-4)m. 2. Nitrogen, carbon monoxide or hydrogen competitively inhibited isocyanide reduction with the following K(i) values: hydrogen, 1.3x10(-3)m; carbon monoxide, 6.8x10(-6)m; nitrogen, 4.3x10(-4)m. 3. Living nitrogen-fixing bacteria, and isolated clover nodules, formed methane from methyl isocyanide. 4. These results are discussed in relation to other work and possible mechanisms of nitrogen fixation.