title: Acid survival of Helicobacter pylori: how does urease activity trigger cytoplasmic pH homeostasis?
abstract: Helicobacter pylori can survive for several hours at pH 1 in the presence of urea. Under these conditions, the organism maintains its cytoplasmic pH at a value close to neutral. The role of the cytoplasmically located urease enzyme in this process is a matter of debate. We propose that cytoplasmic ammonia generated by the action of urease is protonated by H(+) ions leaking in from the acidic medium and that the NH(4)(+) formed is extruded from the cytoplasm via an as-yet-unidentified transport system. This mechanism is compared with the general mechanism of cytoplasmic pH homeostasis in microorganisms.
authors.affiliation: Abteilung Mikrobiologie, Universität Osnabrück, D-49069, Germany. stingl@biologie.uni-osnabrueck.de
authors.forename: Kerstin
authors.initials: K
authors.lastname: Stingl
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Altendorf
authors.forename: Evert P
authors.initials: EP
authors.lastname: Bakker
mesh_terms: D003593:Cytoplasm / Q000737:chemistry / Q000201:enzymology; D016480:Helicobacter pylori / Q000201:enzymology / Q000472:pathogenicity / Q000502:physiology*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D014508:Urea / Q000378:metabolism; D014510:Urease / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D014508:Urea; D014510:Urease