The pyruvate: Ferredoxin oxidoreductase in heterocysts of the cyanobacteriuim Anabaena cylindrica

The Bidirectional NiFe-hydrogenase in Synechocystis sp. PCC 6803 Is Reduced by Flavodoxin and Ferredoxin and Is Essential under Mixotrophic, Nitrate-limiting Conditions

“…NifJ encodes the PFOR, which is known to reduce flavodoxin/ferredoxin to provide electrons for the fixation of nitrogen (36).…”

Anaplerotic reactions in Anabaena cylindrica

“…Acetylcoenzyme A can obviously not be converted to acetate for ATP-formation, as cyanobacteria do not excrete acetate in significant amounts. It is probably converted to citrate as may be deduced from the occurrence of citrate synthase [8]. This, however, requires the supply with oxaloacetate.…”

“…Heterocyst isolation and preparation of exvate carboxylase assay. The decarboxylation of tracts from heterocysts and vegetative cells have malate was performed in Warburg vessels conbeen described earlier [8,13]. Heterocysts were isotaining in 2.…”

“…However, evidence has recently been accumulated from experiments with more intact heterocyst preparations that enzymes of glycolysis and part of the tricarboxylic acid cycle occur in these cells [7]. The demonstration of the 02-sensitive pyruvate : ferredoxin oxidoreductase [8] and glutamine : oxoglutarate amido transferase [9] as well as a rather active isocitrate dehydrogenase with complex regulatory properties [lo] is particularly noteworthy. Thus heterocysts themselves may synthesize glutamate and oxoglutarate.…”

“…Thus heterocysts themselves may synthesize glutamate and oxoglutarate. As an enzyme catalyzing the cleavage of oxoglutarate is absent [8], heterocysts cannot regenerate oxaloacetate by the tricarboxylic acid cycle. They must therefore possess anaplerotic reactions to form oxaloacetate which (ii) Therefore, amphibolic reactions in heterocysts and vegetative cells of Anabaena cylindrica are investigated here.…”