A New Class of Tungsten-Containing Oxidoreductase in Caldicellulosiruptor, a Genus of Plant Biomass-Degrading Thermophilic Bacteria.
Caldicellulosiruptor bescii grows optimally at 78°C and is able to decompose high concentrations of lignocellulosic plant biomass without the need for thermochemical pretreatment. C. bescii ferments both C5 and C6 sugars primarily to hydrogen gas, lactate, acetate, and CO2 and is of particular interest for metabolic engineering applications given the recent availability of a genetic system. Developing optimal strains for technological use requires a detailed understanding of primary metabolism, particularly when the goal is to divert all available reductant (electrons) toward highly reduced products such as biofuels. During an analysis of the C. bescii genome sequence for oxidoreductase-type enzymes, evidence was uncovered to suggest that the primary redox metabolism of C. bescii has a completely uncharacterized aspect involving tungsten, a rarely used element in biology. An active tungsten utilization pathway in C. bescii was demonstrated by the heterologous production of a tungsten-requiring, aldehyde-oxidizing enzyme (AOR) from the hyperthermophilic archaeon Pyrococcus furiosus. Furthermore, C. bescii also contains a tungsten-based AOR-type enzyme, here termed XOR, which is phylogenetically unique, representing a completely new member of the AOR tungstoenzyme family. Moreover, in C. bescii, XOR represents ca. 2% of the cytoplasmic protein. XOR is proposed to play a key, but as yet undetermined, role in the primary redox metabolism of this cellulolytic microorganism.
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Israel M
IM
Scott
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Gabe M
GM
Rubinstein
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Gina L
GL
Lipscomb
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Mirko
M
Basen
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Gerrit J
GJ
Schut
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Amanda M
AM
Rhaesa
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
W Andrew
WA
Lancaster
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Farris L
FL
Poole
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA.
Robert M
RM
Kelly
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA adams@bmb.uga.edu.
Michael W W
MW
Adams
D000447:Aldehydes / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000201:enzymology* / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D020027:Pyrococcus furiosus / Q000201:enzymology / Q000378:metabolism; D014414:Tungsten / Q000378:metabolism*
D000447:Aldehydes; D001426:Bacterial Proteins; D010088:Oxidoreductases; D014414:Tungsten