Biomaterial Database

Uptake hydrogenase activity and ATP formation in Rhizobium leguminosarum bacteroids. 1982

L M Nelson, and S O Salminen

The role of uptake hydrogenase was studied in Rhizobium leguminosarum bacteroids from the nodules of Pisum sativum L. cv. Homesteader. Uptake hydrogenase activity, measured by the 3H2 uptake method, was dependent on O-consumption and was similar to H2 uptake measured by gas chromatography. Km for O2 of 0.0007 atm (0.0709 kPa) and a Km for H2 of 0.0074 atm (0.7498, kPa) were determined. H2 increased the rate of endogenous respiration by isolates with uptake hydrogenase (Hup+) but had no effect on an isolate lacking uptake hydrogenase (Hup-). A survey of 14 Hup+ isolates indicated a wide range of H2 uptake activities. Four of the isolates tested had activities similar to or higher than those found in two Hup+ Rhizobium japonicum strains. H2 uptake was strongly coupled to ATP formation in only 5 of the 14 isolates. H2 increased the optimal O2 level of C2H2 reduction by 0.01 atm and permitted enhanced C2H2 reduction at O2 levels above the optimum in both a coupled and an uncoupled isolate. At suboptimal O2 concentrations a small enhancement of C2H2 reduction by H2 was seen in two out of three isolates in which H2 oxidation was coupled to ATP formation. Thus, the main function of uptake hydrogenase in R. leguminosarum appears to be in the protection of nitrogenase from O2 damage.

UI	MeSH Term	Description	Entries
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010088	Oxidoreductases	The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)	Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D010101	Oxygen Consumption	The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)	Consumption, Oxygen,Consumptions, Oxygen,Oxygen Consumptions
D004980	Ethane	A two carbon alkane with the formula H3C-CH3.
D006859	Hydrogen	The first chemical element in the periodic table with atomic symbol H, and atomic number 1. Protium (atomic weight 1) is by far the most common hydrogen isotope. Hydrogen also exists as the stable isotope DEUTERIUM (atomic weight 2) and the radioactive isotope TRITIUM (atomic weight 3). Hydrogen forms into a diatomic molecule at room temperature and appears as a highly flammable colorless and odorless gas.	Protium,Hydrogen-1
D006864	Hydrogenase	An enzyme found in bacteria. It catalyzes the reduction of FERREDOXIN and other substances in the presence of molecular hydrogen and is involved in the electron transport of bacterial photosynthesis.	Ferredoxin Hydrogenase,H2-Oxidizing Hydrogenase,Hydrogenlyase,H2 Oxidizing Hydrogenase,Hydrogenase, Ferredoxin,Hydrogenase, H2-Oxidizing
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D012231	Rhizobium	A genus of gram-negative, aerobic, rod-shaped bacteria that activate PLANT ROOT NODULATION in leguminous plants. Members of this genus are nitrogen-fixing and common soil inhabitants.