PHOSPHOENOLPYRUVATE CARBOXYLASE FROM ACETOBACTER-ACETI

In Acetobacter aceti growing on pyruvate as the only source of carbon and energy, oxaloacetate (OAA) is produced by a phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31). The enzyme was purified 122-fold and a molecular weight of about 380,000 was estimated by gel filtration. The optimum pH was 7.5 and the Km values for PEP and NaHCO3 were 0.49 mM and about 3 mM, respectively. The enzyme needed a divalent cation; the Km for Mn2+, Co2+ and Mg2+ were 0.12, 0.26 and 0.77 mM, respectively. Maximal activity was only obtained with Mg2+. Mn2+ and Co2+ became inhibitory at high concentrations. The activity was inhibited by succinate and, to a lesser extent, by fumarate, citrate, α-ketoglutarate, aspartate and glutamate. As compared with the corresponding enzyme from A. xylinum, the PEP carboxylase of A. aceti showed the following differences: a) It had an absolute requirement for acetyl CoA (Ka 0.18 mM) or propionyl CoA (Ka 0.2 mM). b) It was not affected by ADP. c) It was sensitive to thiol blocking agents. © 1979 Springer-Verlag.