Waxmonoester fermentation in Euglena gracilis T. Factors favouring the synthesis of odd-numbered fatty acids and alcohols

Schneider, Tanja; Betz, A.

doi:10.1007/bf00397387

Cited by 46 publications

(46 citation statements)

References 20 publications

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“…Wax ester fermentation by Euglena is similar in general principle to the synthesis of branched shortchain fatty acids in Ascaris or butyrate in Dasytricha: fatty acids are synthesized from acetyl-CoA condensation with an acyl-CoA (starting with acetyl-CoA or propionyl-CoA), a reduction of the resulting 3-oxoacid to 3-hydroxy acid, dehydration thereof, and a reduction of the resulting trans-enoyl-CoA to the elongated acylCoA. In contrast to malonyl-CoA-dependent fatty acid synthesis, the acetyl-CoA-dependent Euglena route allows net fermentative ATP synthesis from glucose, because acetyl-CoA is condensed without prior ATP-dependent carboxylation to malonyl-CoA (213,215,443). The step catalyzed by trans-2-enoyl-CoA reductase (NADPH dependent) circumvents the reversal of an O 2 -dependent step in ␤-oxidation (197).…”

Section: Fig 13mentioning

confidence: 99%

Biochemistry and Evolution of Anaerobic Energy Metabolism in Eukaryotes

Müller

Mentel

Hellemond

et al. 2012

Microbiol Mol Biol Rev

683

904

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SUMMARY Major insights into the phylogenetic distribution, biochemistry, and evolutionary significance of organelles involved in ATP synthesis (energy metabolism) in eukaryotes that thrive in anaerobic environments for all or part of their life cycles have accrued in recent years. All known eukaryotic groups possess an organelle of mitochondrial origin, mapping the origin of mitochondria to the eukaryotic common ancestor, and genome sequence data are rapidly accumulating for eukaryotes that possess anaerobic mitochondria, hydrogenosomes, or mitosomes. Here we review the available biochemical data on the enzymes and pathways that eukaryotes use in anaerobic energy metabolism and summarize the metabolic end products that they generate in their anaerobic habitats, focusing on the biochemical roles that their mitochondria play in anaerobic ATP synthesis. We present metabolic maps of compartmentalized energy metabolism for 16 well-studied species. There are currently no enzymes of core anaerobic energy metabolism that are specific to any of the six eukaryotic supergroup lineages; genes present in one supergroup are also found in at least one other supergroup. The gene distribution across lineages thus reflects the presence of anaerobic energy metabolism in the eukaryote common ancestor and differential loss during the specialization of some lineages to oxic niches, just as oxphos capabilities have been differentially lost in specialization to anoxic niches and the parasitic life-style. Some facultative anaerobes have retained both aerobic and anaerobic pathways. Diversified eukaryotic lineages have retained the same enzymes of anaerobic ATP synthesis, in line with geochemical data indicating low environmental oxygen levels while eukaryotes arose and diversified.

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Section: Fig 13mentioning

confidence: 99%

Biochemistry and Evolution of Anaerobic Energy Metabolism in Eukaryotes

Müller

Mentel

Hellemond

et al. 2012

Microbiol Mol Biol Rev

683

904

View full text Add to dashboard Cite

show abstract

“…Rhodoquinone Levels in Euglena Change with Oxygen Availability-In wax ester fermentation in Euglena mitochondria, the synthesis of even-numbered fatty acids starts from acetylCoA, whereas odd-numbered fatty acid synthesis starts from propionyl-CoA, which is generated via succinate, propionate, and methylmalonyl-CoA (21,56,57). The formation of propionyl-CoA involves fumarate reductase, which catalyzes the reverse reaction of that in succinate dehydrogenase (complex II) but requires the lower midpoint potential of rhodoquinone versus ubiquinone to function efficiently in the succinate-synthesizing direction (2,13,58,59).…”

Section: Proteomic Studies Reveal An Anaerobic Response In Euglenamentioning

confidence: 99%

Euglena gracilis Rhodoquinone:Ubiquinone Ratio and Mitochondrial Proteome Differ under Aerobic and Anaerobic Conditions

Hoffmeister¹,

Klei

Rotte

et al. 2004

Journal of Biological Chemistry

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Euglena gracilis cells grown under aerobic and anaerobic conditions were compared for their whole cell rhodoquinone and ubiquinone content and for major protein spots contained in isolated mitochondria as assayed by two-dimensional gel electrophoresis and mass spectrometry sequencing. Anaerobically grown cells had higher rhodoquinone levels than aerobically grown cells in agreement with earlier findings indicating the need for fumarate reductase activity in anaerobic wax ester fermentation in Euglena. Microsequencing revealed components of complex III and complex IV of the respiratory chain and the E1␤ subunit of pyruvate dehydrogenase to be present in mitochondria of aerobically grown cells but lacking in mitochondria from anaerobically grown cells. No proteins were identified as specific to mitochondria from anaerobically grown cells. cDNAs for the E1␣, E2, and E3 subunits of mitochondrial pyruvate dehydrogenase were cloned and shown to be differentially expressed under aerobic and anaerobic conditions. Their expression patterns differed from that of mitochondrial pyruvate:NADP ؉ oxidoreductase, the N-terminal domain of which is pyruvate:ferredoxin oxidoreductase, an enzyme otherwise typical of hydrogenosomes, hydrogen-producing forms of mitochondria found among anaerobic protists. The Euglena mitochondrion is thus a long sought intermediate that unites biochemical properties of aerobic and anaerobic mitochondria and hydrogenosomes because it contains both pyruvate:ferredoxin oxidoreductase and rhodoquinone typical of hydrogenosomes and anaerobic mitochondria as well as pyruvate dehydrogenase and ubiquinone typical of aerobic mitochondria. Our data show that under aerobic conditions Euglena mitochondria are prepared for anaerobic function and furthermore suggest that the ancestor of mitochondria was a facultative anaerobe, segments of whose physiology have been preserved in the Euglena lineage.

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“…Although we have provided evidence of a reductive pathway from OAA to succinate in this alga during anaerobiosis, we do not know the relative flux of carbon between the oxidative and reductive paths of the TCAC. We therefore do not know the significance of the reductive pathway in the maintenance of oxidative TCAC carbon flow relative to other potential processes such as H2 evolution (9,10 (16) and in Euglena (27). It has been shown that fumarate reduction may be linked to NADH oxidation and ATP synthesis (7 and references therein) thereby providing an excellent strategy for anaerobic fermentation.…”

Section: Reductive Tcac Carbon Metabolism During Anaerobiosismentioning

confidence: 99%