Early metabolic effects and mechanism of ammonium transport in yeast
Studies were performed to define the effects and mechanism of NH+4 transport in yeast. The following results were obtained. Glucose was a better facilitator than ethanol-H/sub 2/O/sub 2/ for ammonium transport; low concentrations of uncouplers or respiratory inhibitors could inhibit the transport with ethanol as the substrate. With glucose, respiratory inhibitors showed only small inhibitory effects, and only high concentrations of azide or trifluoromethoxy carbonylcyanide phenylhydrazone could inhibit ammonium transport. Ammonium in the free state could be concentrated approximately 200-fold by the cells. Also, the addition of ammonium produced stimulation of both respiration and fermentation; an increased rate of H+ extrusion and an alkalinization of the interior of the cell; a decrease of the membrane potential, as monitored by fluorescent cyanine; an immediate decrease of the levels of ATP and an increase of ADP, which may account for the stimulation of both fermentation and respiration; and an increase of the levels of inorganic phosphate. Ammonium was found to inhibit 86Rb+ transport much less than K+. Also, while K+ produced a competitive type of inhibition, that produced by NH4+ was of the noncompetitive type. From the distribution ratio of ammonium and the pH gradient, an electrochemical potential gradient of around -180 mV was calculated. The results indicate that ammonium is transported in yeast by a mechanism similar to that of monovalent alkaline cations, driven by a membrane potential. The immediate metabolic effects of this cation seem to be due to an increased (H+)ATPase, to which its transport is coupled. However, the carriers seem to be different. The transport system studied in this work was that of low affinity.
- Research Organization:
- Universidad Nacional Autonoma de Mexico, Mexico City
- OSTI ID:
- 6525913
- Journal Information:
- Arch. Biochem. Biophys.; (United States), Vol. 2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMMONIUM COMPOUNDS
MEMBRANE TRANSPORT
METABOLISM
ETHANOL
BIOLOGICAL EFFECTS
AMMONIA
ATP
ATP-ASE
CELL MEMBRANES
FERMENTATION
GLUCOSE
HYDROGEN PEROXIDE
PHOSPHATES
PROTONS
RUBIDIUM 86
SACCHAROMYCES CEREVISIAE
SUBSTRATES
TRACER TECHNIQUES
ACID ANHYDRASES
ALCOHOLS
ALDEHYDES
ALKALI METAL ISOTOPES
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCONVERSION
CARBOHYDRATES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
FUNGI
HADRONS
HEXOSES
HYDRIDES
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MEMBRANES
MICROORGANISMS
MINUTES LIVING RADIOISOTOPES
MONOSACCHARIDES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUCLEI
NUCLEONS
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PEROXIDES
PHOSPHOHYDROLASES
PHOSPHORUS COMPOUNDS
PLANTS
RADIOISOTOPES
RUBIDIUM ISOTOPES
SACCHARIDES
SACCHAROMYCES
YEASTS
550501* - Metabolism- Tracer Techniques
560300 - Chemicals Metabolism & Toxicology