title: Effect of pH on tritium exchange and hydrogen production and uptake in free-living cells and in bacteroids of Bradyrhizobium japonicum.
abstract: Soybean nodule bacteroids and Bradyrhizobium japonicum free-living cells induced for H2-uptake hydrogenase, actively catalyze the evolution of H2 in a reaction highly dependent on the pH. The optimal pHs for the evolution and uptake reactions were 4.0 and 7.5-8.0, respectively. No differences were found between free-living cells and bacteroids with respect to hydrogen acceptor specificity, although absolute rates of H2 uptake were higher for free-living cells. Both types of cells were able to evolve hydrogen from reduced methyl viologen at low pH. These intact cells also catalyzed the exchange reaction between tritium and water in the absence of oxygen. The pH profile of the exchange activity showed two peaks at values near the optimal pHs for the evolution and uptake reactions.
authors.affiliation: Instituto de Catálisis, CSIC, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Barate
authors.forename: P
authors.initials: P
authors.lastname: Reyes
authors.forename: R
authors.initials: R
authors.lastname: Munilla
authors.forename: V M
authors.initials: VM
authors.lastname: Fernández
authors.forename: A
authors.initials: A
authors.lastname: Ballesteros
authors.forename: T
authors.initials: T
authors.lastname: Ruiz-Argüeso
mesh_terms: D001439:Bacteroides / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase / Q000378:metabolism; D014316:Tritium / Q000378:metabolism*
chemical_list: D014316:Tritium; D006859:Hydrogen; D006864:Hydrogenase