Effect of Acetylene and Carbon Monoxide on Hydrogen Uptake and Evolution by Nitrogen-Starved Cultures of Mastigocladus laminosus

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Hydrogen photoevolution by a thermophilic blue-green alga, Mastigocladus laminosus, was investigated with respect to the effect of C_2H_2 and/or CO on nitrogenase and H_2 uptake activities. Nitrogenase activity, which supported H_2 evolution of this alga, was increased by one day of nitrogen starvation and thereafter remained at a high level. During the starvation, however, H_2 uptake activity also increased, resulting in a decreased and less sustainable H_2 evolution. This uptake activity was sensitive to C_2H_2 but rather insensitive to CO. When assayed in the presence of C_2H_2 and CO, H_2 evolution in the decreased phase was restored to the maximum value. In the mechanism of the restoration. C_2H_2 and CO seemed to partially inhibit the H_2 uptake catalyzed by hydrogenase and CO blocked all but the proton reducing activity of nitrogenase. In addition, further inhibition of H_2 uptake occurred during incubation with C_2H_2, resulting in further stimulation of H_2 evolution in the presence of both gases, or occurred immediately after several hours of preincubation with C_2H_2. Such a delayed inhibition of H_2 uptake by C_2H_2 did not involve the inhibition of hydrogenase enzyme.
日本植物生理学会の論文