The pyruvate carboxylase of Aspergillus niger.

Woronick and Johnson (1) observed in Aspergillus niger extracts a pyruvate carboxylating system requiring adenosine triphosphate, but not involving phosphopyruvate, and suggested that the carboxylation reaction was coupled with the conversion of adenosine triphosphate to adenosine diphosphate and inorganic phosphate. Utter and Keech (2) studied a similar reaction in extracts of avian and beef liver. They were able to show that such coupling did indeed occur, one mole of adenosine triphosphate being hydrolyzed for each mole of oxaloacetate formed. With their preparations, catalytic amounts of acetyl coenzyme A were necessary. The carboxylation reaction was inhibited by avidin. Fuller and Kornberg (3) have observed an acetyl coenzyme A-catalyzed, adenosine triphosphate-dependent pyruvate carboxylation in Chromatium extracts. Seubert and Remberger (4) have recently purified a pyruvate-carboxylating enzyme from Pseudomonas citronellolis. They have presented evidence that its mechanism of action is similar to that of P-methylcrotonyl carboxylase (5). This carboxylase and propionyl carboxylase (6) require as substrate the coenzyme A derivative of the acid to be carboxylated. The pyruvic carboxylase from Pseudomonas, however, is active on pyruvate ion. Since the pyruvic carboxylases from liver (2) and Chromatium (3) were found to require catalytic amounts of acetyl coenzyme A, it might be concluded that the active form of the substrate is pyruvyl coenzyme A, regenerated by coenzyme A transfer from oxaloacetyl coenzyme A to pyruvate. It was considered of interest to determine to what degree the pyruvate carboxylase of Aspergillus (1) resembled the pyruvate carboxylases from other sources.