Ferredoxin-dependent carbon assimilation in Rhodospirillum rubrum.

Abstract

Evidence has been presented that a soluble fraction from R. rubrum cells contains two new primary carboxylation reactions which depend on the reducing power of ferredoxin: (a) pyruvate synthase which brings about a synthesis of pyruvate from acetyl-CoA and CO2 and (b) α-ketoglutarate synthase which brings about a synthesis of α-ketoglutarate from succinyl-CoA and CO2. The soluble fraction of R. rubrum cells contains also a series of other enzymes which, together with the ferredoxin-dependent enzymes, constitutes a reductive carboxylic acid cycle—a new cyclic pathway for CO2 assimilation that was first found in the photosynthetic bacterium, Chlorobium thiosulfatophilum.