title: Sodium ion pumps and hydrogen production in glutamate fermenting anaerobic bacteria.
abstract: Anaerobic bacteria ferment glutamate via two different pathways to ammonia, carbon dioxide, acetate, butyrate and molecular hydrogen. The coenzyme B12-dependent pathway in Clostridium tetanomorphum via 3-methylaspartate involves pyruvate:ferredoxin oxidoreductase and a novel enzyme, a membrane-bound NADH:ferredoxin oxidoreductase. The flavin- and iron-sulfur-containing enzyme probably uses the energy difference between reduced ferredoxin and NADH to generate an electrochemical Na+ gradient, which drives transport processes. The other pathway via 2-hydroxyglutarate in Acidaminococcus fermentans and Fusobacterium nucleatum involves glutaconyl-CoA decarboxylase, which uses the free energy of decarboxylation to generate also an electrochemical Na+ gradient. In the latter two organisms, similar membrane-bound NADH:ferredoxin oxidoreductases have been characterized. We propose that in the hydroxyglutarate pathway these oxidoreductases work in the reverse direction, whereby the reduction of ferredoxin by NADH is driven by the Na+ gradient. The reduced ferredoxin is required for hydrogen production and the activation of radical enzymes. Further examples show that reduced ferredoxin is an agent, whose reducing energy is about 1 ATP 'richer' than that of NADH.
authors.affiliation: Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Marburg, Germany.
authors.forename: Clara D
authors.initials: CD
authors.lastname: Boiangiu
authors.forename: Elamparithi
authors.initials: E
authors.lastname: Jayamani
authors.forename: Daniela
authors.initials: D
authors.lastname: Brügel
authors.forename: Gloria
authors.initials: G
authors.lastname: Herrmann
authors.forename: Jihoe
authors.initials: J
authors.lastname: Kim
authors.forename: Lucia
authors.initials: L
authors.lastname: Forzi
authors.forename: Reiner
authors.initials: R
authors.lastname: Hedderich
authors.forename: Irini
authors.initials: I
authors.lastname: Vgenopoulou
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Pierik
authors.forename: Julia
authors.initials: J
authors.lastname: Steuber
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buckel
mesh_terms: D000595:Amino Acid Sequence; D001421:Bacteria, Anaerobic / Q000201:enzymology*; D001693:Biological Transport, Active; D005971:Glutamates / Q000378:metabolism*; D005977:Glutarates / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D016623:Ion Pumps / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism
chemical_list: D005971:Glutamates; D005977:Glutarates; D016623:Ion Pumps; C019417:alpha-hydroxyglutarate; D006859:Hydrogen; D012964:Sodium