EVIDENCE FOR NICKEL IN THE SOLUBLE HYDROGENASE FROM THE UNICELLULAR GREEN-ALGA SCENEDESMUS-OBLIQUUS

Cultures of the green alga Scenedesmus obliquus were grown in the pres ence of either the chelating reagent EDTA or NiCl2, in various concent rations and assayed for hydrogenase catalyzed photohydrogen evolution after an anaerobic dark adaptation period. Cultivation of algae in the presence of 100 mu M EDTA inhibited the formation of hydrogenase acti vity by 37%. After a cultivation of the cells in the presence of 5-20 mu M NiCl2, photohydrogen evolution was increased by 20-40%. Addition of EDTA up to a final concentration of 1.5 mM had no effect on the act ivity of hydrogenase in cell-free hydrogenase preparations. Cultures g rown in the presence of radioactive (NiCl2)-Ni-63, incorporated Ni-63 in a parallel fashion to the cell growth. In radioactive labeled hydro genase preparations a co-elution of radioactivity and hydrogenase acti vity could be observed using gel filtration chromatography.