Characterization and partial purification of the reversible hydrogenase of Anabaena cylindrica

Abstract

Three types of hydrogenases are recognized in the literature; a reversible hydrogenase which has been highly purified and characterized from saccharolytic bacteria [ 11, an uptake hydrogenase which is seemingly incapable of evolving hydrogen and differs from the reversible hydrogenase in being saturated at low pH2 [2], and the ATP-driven hydrogen evolution catalyzed by nitrogenase in the absence of other reducible substrates [3]. Species of cyanobacteria such as Anabaena cylindrica contain all three types of hydrogenase under some conditions [4]. Hydrogen evolution by nitrogenase in this organism has been studied in some detail [5-71. The presence of an uptake hydrogenase, similar to the Azofobacter hydrogenase, has been demonstrated [&lo]. The presence of reversible hydrogenase activity can be directly shown with cultures of A. cylindrica that lack nitrogenase activity either through growth in the presence of tungsten instead of molybdenum, or through ammonium repression [ 11 ,12 1. Hydrogen is produced by isolated heterocysts or vegetative cell fragments supplied with artificial electron donors [ 131. In [ 14,151 crude extracts with hydrogenase activity were prepared from nitrate-grown cultures of A. cylindrica incubated anaerobically in the dark under an atmosphere of hydrogen. It was found that phenazine methosulphate, methylene blue, dichlorophenol-indophenol and toluidine blue were effective as electron acceptors, but the results suggested that redox coupling between the hydrogenase and ferredoxin had a very low efficiency. When crude extracts