title: Distinct physiological roles for the two L-asparaginase isozymes of Escherichia coli.
abstract: Escherichia coli expresses two L-asparaginase (EC 3.5.1.1) isozymes: L-asparaginse I, which is a low affinity, cytoplasmic enzyme that is expressed constitutively, and L-asparaginase II, a high affinity periplasmic enzyme that is under complex co-transcriptional regulation by both Fnr and Crp. The distinct localisation and regulation of these enzymes suggest different roles. To define these roles, a set of isogenic mutants was constructed that lacked either or both enzymes. Evidence is provided that L-asparaginase II, in contrast to L-asparaginase I, can be used in the provision of an anaerobic electron acceptor when using a non-fermentable carbon source in the presence of excess nitrogen.
authors.affiliation: Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Yogitha N
authors.initials: YN
authors.lastname: Srikhanta
authors.forename: John M
authors.initials: JM
authors.lastname: Atack
authors.forename: Ifor R
authors.initials: IR
authors.lastname: Beacham
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
mesh_terms: D000693:Anaerobiosis; D001215:Asparaginase / Q000235:genetics / Q000502:physiology*; D001216:Asparagine / Q000378:metabolism; D003470:Culture Media / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology; D004579:Electron Transport; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005650:Fumarates / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D003470:Culture Media; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D005650:Fumarates; D007506:Iron-Sulfur Proteins; D007527:Isoenzymes; C481662:crp protein, E coli; D001216:Asparagine; D000242:Cyclic AMP; D001215:Asparaginase; D009584:Nitrogen
keywords: Anaerobic growth; Asparaginase; Escherichia coli; Isozymes