Characteristics of nitrogenase activity in broken cell preparations of the blue-green alga Gloeocapsa sp. LB 795

Broken cell preparations of the blue-green alga Gloeocapsa sp. LB 795 reduce acetylene to ethylene and evolve hydrogen in the presence of sodium dithionite and adenosine triphosphate (ATP). The enzyme system is almost completely inhibited by adenosine diphosphate (ADP) (7.5 mM), O2 and CO (0.01 atm), and CO2 (0.05 atm). Its kinetic properties are very similar to those of nitrogenases from other sources, but, unlike the enzymes so far isolated from other blue-green algae, Gloeocapsa nitrogenase is sedimented by centrifugation at 10 000 g.