Reduction of Cyanide and Isocyanide by Nitrogenase of <i>Azotobacter chroococcum</i>

Abstract

Burns & Bulen (1965) showed that cell-free extracts of Azotobacter vinelandii contained an ATP-activated system capable of fixing nitrogen. When provided with sodium dithionite and an ATP- generating system, their preparations evolved less hydrogen under nitrogen than under argon, the difference being accountable as nitrogen reduced to ammonia. Hardy & Knight (1966b) showed that dithionitedependent adenosine-triphosphatase activity was associated with nitrogen fixation. More recently preparations from A. vinetandii and Cloetridium pa8teurianum have been found to reduce a variety of additional substrate including acetylene (Dilworth, 1966), nitrous oxide, N3-and CN-ions (Hardy & Knight,1966a). We now report that nitrogen-fixing extracts of Azotobacter chroo- coccum reduce not only CN-ions but also methyl isocyanide, and indicate the relevance of these reactions to the mechanism of nitrogen fixation.