Electron transport phosphorylation driven by glyoxylate respiration with hydrogen as electron donor in membrane vesicles of a glyoxylate-fermenting bacterium.
The syntrophically glycolate-fermenting bacterium in the methanogenic binary coculture FlGlyM was isolated in pure culture (strain FlGlyR) with glyoxylate as sole substrate. This strain disproportionated 12 glyoxylate to 7 glycolate, 10 CO2, and 3 hydrogen. Glyoxylate was oxidized via the malyl-CoA pathway. All enzymes of this pathway, i.e. malyl-CoA lyase/malate: CoA ligase, malic enzyme, and pyruvate synthase, were demonstrated in cell-free extracts. Glycolate dehydrogenase, hydrogenase, and ATPase, as well as menaquinones as potential electron carriers, were present in the membranes. Everted membrane vesicles catalyzed hydrogen-dependent glyoxylate reduction to glycolate [86-207 nmol min-1 (mg protein)-1] coupled to ATP synthesis from ADP and Pi [38-82 nmol min-1 (mg protein)-1)]. ATP synthesis was abolished entirely by protonophores or ATPase inhibitors (up to 98 and 94% inhibition, respectively) indicating the involvement of proton-motive force in an electron transport phosphorylation driven by a new glyoxylate respiration with hydrogen as electron donor. Measured reaction rates in vesicle preparations revealed a stoichiometry of ATP formation of 0.2-0.5 ATP per glyoxylate reduced.
Friedrich
M
M
Fakultät für Biologie, Universität Konstanz, Germany.
Schink
B
B
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D004579:Electron Transport / Q000502:physiology; D019605:Euryarchaeota / Q000166:cytology / Q000201:enzymology / Q000302:isolation & purification / Q000502:physiology*; D006038:Glyoxylates / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010766:Phosphorylation
D006038:Glyoxylates; D009249:NADP; D000255:Adenosine Triphosphate; C031150:glyoxylic acid