OXALOACETATE DECARBOXYLATION AND OXALOACETATE-CARBON DIOXIDE EXCHANGE IN ACETOBACTER XYLINUM

Abstract

Benziman, Moshe (The Hebrew University of Jerusalem, Jerusalem, Israel), and N. Heller . Oxaloacetate decarboxylation and oxaloacetate-carbon dioxide exchange in Acetobacter xylinum . J. Bacteriol. 88: 1678–1687. 1964.—Extracts of Acetobacter xylinum , prepared by sonic treatment, were shown to catalyze the decarboxylation of oxaloacetate (OAA) to pyruvate and CO 2 , and the exchange of C 14 -carbon dioxide into the β-carboxyl of OAA. Fractionation of the extracts with ammonium sulfate resulted in a 10-fold increase of the specific activity of the enzyme system catalyzing the CO 2 exchange and OAA decarboxylation reactions. The purified preparation catalyzed the exchange of pyruvate- 3-C 14 into OAA. Similar pH curves with a pH optimum of 5.6 were obtained for the CO 2 exchange and OAA decarboxylation reactions. Both reactions require the presence of Mn 2+ or Mg 2+ ions. OAA decarboxylation was more strongly inhibited than the exchange of CO 2 by dialysis or metal-chelating agents. Avidin did not inhibit either reaction. Adenosine triphosphate (ATP), adenosine diphosphate (ADP), guanosine triphosphate (GTP), guanosine diphosphate (GDP), pyrophosphate, or inorganic phosphate did not promote OAA decarboxylation and the CO 2 -exchange reaction catalyzed by the purified preparation. The purified preparation failed to catalyze the carboxylation of phosphoenolpyruvate in the presence of GDP, ADP, or inorganic phosphate, and that of pyruvate in the presence of ATP or GTP, even when supplemented with an OAA-trapping system. A scheme for OAA decarboxylation which could account for the observed exchange reactions and for the failure to obtain net fixation of CO 2 is proposed. The relation between the exchange reaction and the synthesis of cellulose from pyruvate by A. xylinum is discussed.