Fumarate breathing

Under Fumaratatmung is meant an anaerobic respiration , in which no oxygen , but C ₄ dicarboxylate (usually fumarate or fumaric acid ) as the electron acceptor functions. One molecule of fumarate is reduced to one molecule of succinate ( succinic acid ) for energy production.

Fumarate breathing provides comparatively little energy (redox potential E ^{o '} + 0.03 V with fumarate breathing compared to + 0.82 V with aerobic breathing).

Occurrence

Fumarate breathing can be used by facultative anaerobes. Only prokaryotes are able to do this , especially archaea and eubacteria as inhabitants of moist locations (water sediments or in groundwater-bearing layers or in waterlogged or cloacal in animal organisms) such as Escherichia coli .

Many endoparasites, such as tapeworms , also appear to be facultative anaerobes and can take advantage of fumarate breathing. However, the anaerobic metabolic capacity goes back to symbiotic bacteria, which provide the energy conversion.

Metabolic regulation

E. coli is a facultative anaerobe. The decision between aerobic and anaerobic metabolism is made by the global regulator Fnr (fumarate / nitrate regulator). In the absence of oxygen it induces the gene expression of all anaerobic metabolic enzymes, under aerobic conditions Fnr is inactive. In order to be able to use different substrates as electron acceptors, different enzymes must be available to the metabolism.

The control transcriptional gene expression for the Fumaratatmung supplies the two-component system DcuSR consisting of the S ensor component DcuS (a membrane- histidine for substrate recognition) and the R esponseregulator Dcur (a cytoplasmic mechanism for signal transduction ). DcuSR is activated when DcuS perceives C ₄ dicarboxylate in the external medium , but no other usable energy source .

metabolism

Special proteins or enzymes are required for fumarate breathing : a membrane-bound terminal oxidoreductase , the fumarate reductase FrdABCD , which is identical in some subunits to the succinate dehydrogenase . In addition, the fumarate / succinate antiporter DcuB (transport protein) is required to absorb the fumarate from the surrounding medium.

Individual evidence

↑ J. Zenka, J. Prokopic: Contribution to the knowledge of aerobic processes in Taenia crassiceps larvae . In: Folia Parasitol (Praha). 1986; 33 (4), pp. 331-336. (Respiration of homogenates and isolated mitochondria of T. crassiceps larvae was measured. Respiration (about 70%) could be inhibited by cyanide, indicating that an important part is played by classical respiratory chain. When succinate was used as substrate, relatively low respiratory rates were measured, mitochondria showing higher affinity to NADH. Above a half of respiratory rate remained unchanged even at very low oxygen concentrations. Fumarate exhibited inhibitory activity on respiration of T. crassiceps mitochondria. Respiration in which NADH was used as substrate was twice as much more sensitive to inhibition by fumarate than respiration stimulated by succinate.) PMID 3804084
↑ J. Zenka, J. Prokopic: Malic enzyme, malate dehydrogenase, fumarate reductase and succinate dehydrogenase in the larvae of Taenia crassiceps. (Malate dehydrogenase, malic enzyme, succinate dehydrogenase, and fumarate reductase activities have been studied in the cytoplasm and mitochondria of Taenia crassiceps larvae. The results show that these larvae contain enzymes for anaerobic acquisition of energy with terminal fumarate reductase, but some facts, as the high ratio of succinate dehydrogenase activity to fumarate reductase activity and the low proportion of fumarate reductase in the whole NADH oxidase activity in mitochondria, suggest that aerobic processes are also involved in the energy acquisition in this parasite.) PMID 3596392
^ Joseph W. Lengeler: Biology of the Prokaryotes. Thieme 1999, ISBN 3-13-108411-1 , pp. 525f.
↑ Holger Kneuper: Structure and function studies of the C ₄ dicarboxylate sensor DcuS . Dissertation, Johannes Gutenberg University Mainz, August 2005
↑ Evelyn Zientz: Identification and characterization of the fumarate regulation system DcuSR from Escherichia coli . (PDF) Vaam PhD award BIOspektrum 4/01 (7)

[1] J. Zenka, J. Prokopic: Contribution to the knowledge of aerobic processes in Taenia crassiceps larvae . In: Folia Parasitol (Praha). 1986; 33 (4), pp. 331-336. (Respiration of homogenates and isolated mitochondria of T. crassiceps larvae was measured. Respiration (about 70%) could be inhibited by cyanide, indicating that an important part is played by classical respiratory chain. When succinate was used as substrate, relatively low respiratory rates were measured, mitochondria showing higher affinity to NADH. Above a half of respiratory rate remained unchanged even at very low oxygen concentrations. Fumarate exhibited inhibitory activity on respiration of T. crassiceps mitochondria. Respiration in which NADH was used as substrate was twice as much more sensitive to inhibition by fumarate than respiration stimulated by succinate.) PMID 3804084

[2] J. Zenka, J. Prokopic: Malic enzyme, malate dehydrogenase, fumarate reductase and succinate dehydrogenase in the larvae of Taenia crassiceps. (Malate dehydrogenase, malic enzyme, succinate dehydrogenase, and fumarate reductase activities have been studied in the cytoplasm and mitochondria of Taenia crassiceps larvae. The results show that these larvae contain enzymes for anaerobic acquisition of energy with terminal fumarate reductase, but some facts, as the high ratio of succinate dehydrogenase activity to fumarate reductase activity and the low proportion of fumarate reductase in the whole NADH oxidase activity in mitochondria, suggest that aerobic processes are also involved in the energy acquisition in this parasite.) PMID 3596392

[3] Joseph W. Lengeler: Biology of the Prokaryotes. Thieme 1999, ISBN 3-13-108411-1 , pp. 525f.

[4] Holger Kneuper: Structure and function studies of the C ₄ dicarboxylate sensor DcuS . Dissertation, Johannes Gutenberg University Mainz, August 2005

[5] Evelyn Zientz: Identification and characterization of the fumarate regulation system DcuSR from Escherichia coli . (PDF) Vaam PhD award BIOspektrum 4/01 (7)