Phosphoenolpyruvate carboxylation and aspartate synthesis in Acetobacter suboxydans.

Dialyzed extracts of Acetobacter suboxydans ATCC 621 catalyze (14)CO(2) assimilation in the presence of phosphoenolpyruvate and a divalent cation. The formation of (14)C-oxalacetate was demonstrated and found not to be dependent upon the presence of orthophosphate or diphosphonucleotides. Oxalacetate synthesis was stimulated by orthophosphate and inhibited by aspartate. All attempts to demonstrate a reversible carboxylation mechanism have failed. (14)C-aspartate was synthesized when phosphoenolpyruvate, H(14)Co(3) (-), pyridoxal phosphate, and glutamate were added to dialyzed extracts. Chromatographic and spectrophotometric analyses and chemical degradation further demonstrate the presence of a reversible aspartate aminotransferase. The function of oxalacetate synthesis in a bacterium that reportedly lacks an operative tricarboxylic acid cycle is discussed.