Energy-linked pyridine nucleotide transhydrogenase activity in photosynthetically grown Rhodopseudomonas palustris.

Rhodopseudomonas palustris (ATCC 17001) develops energy-dependent NADP+ transhydrogenase activity while growing photosynthetically on thiosulfate, formate, or acetate as the electron donors. The enzymatic activity is present in the supernatant fraction S-144 000. -- As reported, this fraction contains small membrane fragments but no closed vesicles and was shown to drive energy-dependent reversed electron flow as well as an aerobic respiratory electron transport. The energy-dependent transhydrogenase reaction in this fraction can be driven either by ATP, ADP, or inorganic pyrophosphate, but also by acetyl phosphate or acetyl-coenzyme A in the presence of orthophosphate. -- Arsenate acts as an inhibitor and decreases preferentially the acetyl-coenzyme A-dependent and the acetyl phosphate-driven reaction; whereas, oligomycin inhibits preferentially the ATP- and the acetyl phosphate-dependent reactions. -- Acetate kinase and a phosphotransacetylase are operative in S-144 000.