title: The phosphoenolpyruvate carboxykinase also catalyzes C3 carboxylation at the interface of glycolysis and the TCA cycle of Bacillus subtilis.
abstract: Quantitative physiological characterization and isotopic tracer experiments revealed that pyruvate kinase mutants of Bacillus subtilis produced significantly more CO(2) from glucose in the tricarboxylic acid cycle than is explained by the remaining conversion of phosphoenolpyruvate (PEP) to pyruvate catalyzed by the phosphotransferase system. We show here that this additional catabolic flux into the tricarboxylic acid cycle was catalyzed by the PEP carboxykinase. In contrast to its normal role in gluconeogenesis, PEP carboxykinase can operate in the reverse direction from PEP to oxaloacetate upon knockout of pyruvate kinase in a riboflavin-producing B. subtilis strain and in wild-type 168. At least in the industrial strain, we demonstrate the additional capacity of PEP carboxykinase to function as a substitute anaplerotic reaction when the normal pyruvate carboxylase is inactivated. Presumably as a consequence of the unfavorable kinetics of an ATP-synthesizing anaplerotic PEP carboxykinase reaction, such pyruvate carboxylase mutants grow slowly or, as in the case of wild-type 168, not at all.
authors.affiliation: Institute of Biotechnology, Swiss Federal Institute of Technology Zurich (ETH) ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Nicola
authors.initials: N
authors.lastname: Zamboni
authors.forename: Hannu
authors.initials: H
authors.lastname: Maaheimo
authors.forename: Thomas
authors.initials: T
authors.lastname: Szyperski
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Hohmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Sauer
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology*; D005943:Gluconeogenesis / Q000235:genetics / Q000502:physiology; D006019:Glycolysis / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D062907:Oxaloacetic Acid / Q000378:metabolism*; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D062907:Oxaloacetic Acid; D019764:Phosphoenolpyruvate Carboxykinase (ATP)