title: The urea cycle of Helicobacter pylori.
abstract: The presence and activities of the enzymes of the urea cycle in the bacterium Helicobacter pylori were investigated employing one- and two-dimensional NMR spectroscopy and radioactive tracer analysis. Cell suspensions, lysates and membrane preparations generated L-ornithine and ammonium at high rates in incubations with L-arginine, indicating the presence of arginase activity. Anabolic ornithine transcarbamoylase (OTCase) activity was identified by the formation of heat-stable products in incubations of cell-free extracts with ornithine and radiolabelled carbamoyl phosphate. The heat-labile product that resulted from incubations of cell-free extracts with citrulline radiolabelled in the guanidino moiety revealed the presence of catabolic OTCase activity. Argininosuccinate formation and catalysis indicated the presence of argininosuccinate synthetase and argininosuccinase activities. The findings suggested that H. pylori has a urea cycle which acts as an effective mechanism to extrude excess nitrogen from cells.
authors.affiliation: School of Biochemistry, University of New South Wales, Sydney, Australia. G.Mendz@unsw.EDU.AU
authors.forename: G L
authors.initials: GL
authors.lastname: Mendz
authors.forename: S L
authors.initials: SL
authors.lastname: Hazell
mesh_terms: D001120:Arginine / Q000378:metabolism; D001123:Argininosuccinate Lyase / Q000378:metabolism; D001124:Argininosuccinate Synthase / Q000378:metabolism; D001125:Argininosuccinic Acid / Q000378:metabolism; D002221:Carbamyl Phosphate / Q000378:metabolism; D016480:Helicobacter pylori / Q000201:enzymology / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009952:Ornithine / Q000096:biosynthesis; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism; D013997:Time Factors; D014508:Urea / Q000378:metabolism*
chemical_list: D001125:Argininosuccinic Acid; D002221:Carbamyl Phosphate; D014508:Urea; D001120:Arginine; D009952:Ornithine; D009954:Ornithine Carbamoyltransferase; D001123:Argininosuccinate Lyase; D001124:Argininosuccinate Synthase; D009584:Nitrogen