scholarly journals Identification of a Novel Fumarate Reductase Potentially Involved in Electron Bifurcation

2019 ◽  
Author(s):  
Richard Van Kranenburg ◽  
Jeroen Girwar Koendjbiharie
Keyword(s):  
Succinic Acid ◽  
Disulfide Bond ◽  
Fumarate Reductase ◽  
Thiol Groups ◽  
Additional Energy ◽  
Fumarate Respiration

In the succinic acid-producing bacterium Pseudoclostridium thermosuccinogenes the fumarate reductase (FRD) genes reside in an operon together with those encoding an electron bifurcating complex (FlxABCD-HdrABC) that shuttles electrons from NADH to ferredoxin and a disulfide bond. Based on phylogeny and genomic co-occurrence we propose two hypothetical mechanisms via which the FRD is involved in electron bifurcation: (I) A disulfide bond from a hitherto unknown cofactor is reduced by the electron-bifurcating FlxABCD-HdrABC complex, using NADH to generate two thiol groups, while facilitating the unfavourable reduction of ferredoxin by NADH. The disulfide bond is subsequently regenerated via the reduction of fumarate by the FRD using the previously formed thiol groups. (II) The FRD forms an integral part of the FlxABCD-HdrABC complex, and NADH is used to reduce ferredoxin and fumarate directly, without an intermediate disulfide-forming cofactor. Either way enables the conservation of additional energy by a soluble FRD, analogous to fumarate respiration.

scholarly journals Succinate dehydrogenase functioning by a reverse redox loop mechanism and fumarate reductase in sulphate-reducing bacteria

Microbiology ◽  
2006 ◽  
Vol 152 (8) ◽  
pp. 2443-2453 ◽  
Author(s):  
Tanja Zaunmüller ◽  
David J. Kelly ◽  
Frank O. Glöckner ◽  
Gottfried Unden
Keyword(s):  
Succinate Dehydrogenase ◽  
Draft Genome ◽  
Desulfovibrio Desulfuricans ◽  
Geobacter Sulfurreducens ◽  
Fumarate Reductase ◽  
Desulfovibrio Vulgaris ◽  
Succinate Oxidation ◽  
Proton Potential ◽  
Fumarate Respiration ◽  
Reducing Bacteria

Sulphate- or sulphur-reducing bacteria with known or draft genome sequences (Desulfovibrio vulgaris, Desulfovibrio desulfuricans G20, Desulfobacterium autotrophicum [draft], Desulfotalea psychrophila and Geobacter sulfurreducens) all contain sdhCAB or frdCAB gene clusters encoding succinate : quinone oxidoreductases. frdD or sdhD genes are missing. The presence and function of succinate dehydrogenase versus fumarate reductase was studied. Desulfovibrio desulfuricans (strain Essex 6) grew by fumarate respiration or by fumarate disproportionation, and contained fumarate reductase activity. Desulfovibrio vulgaris lacked fumarate respiration and contained succinate dehydrogenase activity. Succinate oxidation by the menaquinone analogue 2,3-dimethyl-1,4-naphthoquinone depended on a proton potential, and the activity was lost after degradation of the proton potential. The membrane anchor SdhC contains four conserved His residues which are known as the ligands for two haem B residues. The properties are very similar to succinate dehydrogenase of the Gram-positive (menaquinone-containing) Bacillus subtilis, which uses a reverse redox loop mechanism in succinate : menaquinone reduction. It is concluded that succinate dehydrogenases from menaquinone-containing bacteria generally require a proton potential to drive the endergonic succinate oxidation. Sequence comparison shows that the SdhC subunit of this type lacks a Glu residue in transmembrane helix IV, which is part of the uncoupling E-pathway in most non-electrogenic FrdABC enzymes.

scholarly journals Succinic Acid Production by Rumen Bacteria. III. Enzymic Studies on the Formation of Succinate by Ruminococcus Flavefaciens

1969 ◽  
Vol 22 (6) ◽  
pp. 1413 ◽  
Author(s):  
MF Hopgood ◽  
DJ Walker
Keyword(s):  
Succinic Acid ◽  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Acid Production ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fumarate Hydratase ◽  
Fumarate Reductase ◽  
Rumen Bacteria ◽  
Succinate Dehydrogenase Activity ◽  
Succinic Acid Production

Enzymes involved in succinic acid production by strain C of R. ftavefacien8 were investigated in cell-free extracts. The results indicate that phosphoenolpyruvate is carboxylated by a phosphoenolpyruvate carboxykinase which uses GDP as phosphate acceptor, and that the oxaloacetate so formed is converted to succinate via a DPNH-dependent malate dehydrogenase, a fumarate hydratase, and a DPNH-dependent fumarate reductase. Succinate dehydrogenase activity was also observed which differed markedly from fumarate reductase in that DPN+ was not reduced and in inhibition characteristics.

scholarly journals Free thiol groups are essential for infectivity of human cytomegalovirus

1999 ◽  
Vol 80 (11) ◽  
pp. 2861-2865 ◽  
Author(s):  
Ali Mirazimi ◽  
Mehrdad Mousavi-Jazi ◽  
Vivi-Anne Sundqvist ◽  
Lennart Svensson
Keyword(s):  
Human Cytomegalovirus ◽  
Disulfide Bond ◽  
Virus Entry ◽  
Bond Formation ◽  
Reducing Agent ◽  
Disulfide Bond Formation ◽  
Thiol Groups ◽  
Nitrobenzoic Acid ◽  
Free Thiol

The membrane-impermeable thiol blocker 5′5-dithiobis 2- nitrobenzoic acid (DTNB) blocked infectivity of human cytomegalovirus (CMV) although the virus still bound to cells. DTNB-treated CMV regained 65% of its infectivity after incubation with the disulfide bond-reducing agent dithiothreitol. These observations suggest that free thiol groups on CMV are required for infectivity and may participate in disulfide bond formation during virus entry.

scholarly journals Amino Acid Sequences Containing Half-Cystine Residues in Ovalbumin

1978 ◽  
Vol 31 (5) ◽  
pp. 433 ◽  
Author(s):  
EOP Thompson ◽  
WK Fisher
Keyword(s):  
Amino Acid ◽  
Disulfide Bond ◽  
Amino Acid Sequences ◽  
Thiol Groups

Ovalbumin is known to have six half-cystine residues with four thiol groups and one disulfide bond.

The metabolism of [14C]bicarbonate byStreptococcus lactis: the synthesis of succinic acid

1978 ◽  
Vol 45 (3) ◽  
pp. 423-431 ◽  
Author(s):  
Alan J. Hillier ◽  
G. Richard Jago
Keyword(s):  
Energy Source ◽  
Succinic Acid ◽  
Fumarate Reductase ◽  
Argininosuccinate Synthetase ◽  
Whole Cells ◽  
Purine Bases ◽  
Streptococcus Lactis ◽  
Adenylosuccinate Synthetase ◽  
Lyase Activity

SummaryWhole cells ofStreptococcus lactisC10, when incubated with an energy source, converted fumarate to succinate and malate to lactate. Cell-free extracts ofStr. lactisC10 contained fumarate reductase, but no aspartase, adenylosuccinate synthetase and lyase or argininosuccinate synthetase and lyase activity could be detected. Cells grown in the presence of [14C]bicarbonate produced labelled succinate during the synthesis of purine bases. However, the amount of succinate produced by this pathway only accounted for approximately one-sixth of the succinate produced by the cells.

Bioavailability of naringenin chalcone in humans after ingestion of cherry tomatoes

2020 ◽  
Vol 90 (5-6) ◽  
pp. 411-416 ◽  
Author(s):  
Carina Kolot ◽  
Ana Rodriguez-Mateos ◽  
Rodrigo Feliciano ◽  
Katharina Bottermann ◽  
Wilhelm Stahl
Keyword(s):  
Plasma Levels ◽  
Average Concentration ◽  
Biologically Active ◽  
Thiol Groups ◽  
Structural Element ◽  
Active Molecule ◽  
Reactive Center ◽  
Average Maximum ◽  
Alpha Beta ◽  
Cherry Tomatoes

Abstract. Chalcones are a type of flavonoids characterized by an α-β unsaturated structural element which may react with thiol groups to activate pathways such as the Nrf2-Keap-1 system. Naringenin chalcone is abundant in the diet but little is known about its bioavailability. In this work, the bioavailability of naringenin chalcone from tomatoes was investigated in a group of healthy men (n=10). After ingestion of 600 grams of tomatoes providing a single dose of 17.3 mg naringenin chalcone, 0.2 mg of naringenin, and 195 mg naringin plasma levels of free and conjugated naringenin and naringenin chalcone (glucuronide and sulfate) were analyzed by UHPLC-QTOF-MS at 0.5, 1, 3, and 6 h post-consumption. Plasma levels of conjugated naringenin increased to about 12 nmol/L with a maximum at about 3 h. Concentrations of free naringenin hardly elevated above baseline. Plasma levels of free and conjugated naringenin chalcone significantly increased. A maximum of the conjugated chalcone was reached at about 3 h after ingestion with an average concentration of about 0.5 nmol/L. No free chalcone was detectable at baseline but low amounts of the unconjugated compound could be detected with an average maximum of 0.8 nmol/L at about 1 h after ingestion. The data demonstrate that naringenin chalcone is bioavailable in humans from cherry tomatoes as a dietary source. However, availability is poor and intramolecular cyclisation as well as extended metabolism likely contribute to the inactivation of the reactive alpha-beta unsaturated reactive center as well as the excretion of the biologically active molecule, respectively.

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