Abstract
In cyanobacteria,respiratory and photosynthetic electron transport chains are closely linked each other. It has been demonstrated that several NAD(P)H dehydrogenases are involved in respiratory electron transport and/or cyclic electron transport around photosystem I. However, few of them have been purified and characterized, and some of them have not been identified. Native PAGE analysis revealed that thermophilic cyanobactrium Synechococcus vulcanus contains several NAD(P)H dehydrogenases. Among them, a 140 kDa band (NADH-specific dehydrogenase) and a 80 kDa band (NADPH-specific dehydrogenase) were increased in cells incubated under oxidative stress conditions. This result suggests that these enzymes play some role in protection against oxidative stress conditions, and that they are involved in cyclic electron transport around photosystem I. Both enzymes were purified by using the combination of anion exchange chromatography and electroelution from gel slices after native PAGE. Subunits composition and enzymatic property of these enzymes will be discussed.
