Abstract
In oxygenic photosynthesis, NAD(P)H dehydrogenases are involved in cyclic electron transport around photosystem I, which may play an important role in acclimation to oxidative stress. None of them, however, have been purified and characterized. Native PAGE analysis followed by activity staining for NAD(P)H dehydrogenases revealed that a thermophilic cyanobacterium Thermosynechococcus elongatus contains several NAD(P)H dehydrogenases. Among them, activities of a 140 kDa band and a 70 kDa band were increased significantly in the cells grown under high light intensity in the presence of methyl viologen. This result suggests that these enzymes play roles in protection against oxidative stress, thus they may be involved in cyclic electron transport around photosystem I. Both enzyme complexes were purified by the combination of anion exchange chromatography and electroelution from gel slices after native PAGE. Subunit composition and enzymatic properties of these enzymes will be discussed.
