Structural studies on three flavin‐interacting regions of the flavoprotein subunit of complex II in <i>Ascaris suum</i> mitochondria

Furushima, Rieko; Kita, Kiyoshi; Takamiya, Shinzaburo; Kawai, Kiyoshi; Aoki, Takashi; Okumura, Hiroshi

doi:10.1016/0014-5793(90)81405-d

Cited by 11 publications

(1 citation statement)

References 25 publications

(39 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can now be concluded that these enzyme complexes for fumarate reduction in eukaryotes differ significantly from the prokaryotic type of FRD since (i) all known primary structures of eukaryotic enzyme complexes functioning in vivo in the direction of fumarate reduction demonstrate a higher amino acid sequence similarity to mammalian and E. coli SDHs than to prokaryotic FRD (1,9,42,43); and (ii) eukaryotic complexes that reduce fumarate interact with a benzoquinone (rhodoquinone), whereas prokaryotic FRDs interact with a naphthoquinone (menaquinone). Therefore, in addition to the two known types of enzyme complexes in prokaryotes (SDH and FRD), which differ in primary structure, activity ratio of succinate oxidation and fumarate reduction, diode-like behavior, and interacting quinone, another type of complex exists.…”

Section: Resultsmentioning

confidence: 99%

Rhodoquinone and Complex II of the Electron Transport Chain in Anaerobically Functioning Eukaryotes

Hellemond

Klockiewicz

Gaasenbeek³

et al. 1995

Journal of Biological Chemistry

View full text Add to dashboard Cite

Many anaerobically functioning eukaryotes have an anaerobic energy metabolism in which fumarate is reduced to succinate. This reduction of fumarate is the opposite reaction to succinate oxidation catalyzed by succinate-ubiquinone oxidoreductase, complex II of the aerobic respiratory chain. Prokaryotes are known to contain two distinct enzyme complexes and distinct quinones, menaquinone and ubiquinone (Q), for the reduction of fumarate and the oxidation of succinate, respectively. Parasitic helminths are also known to contain two different quinones, Q and rhodoquinone (RQ). This report demonstrates that RQ was present in all examined eukaryotes that reduce fumarate during anoxia, not only in parasitic helminths, but also in freshwater snails, mussels, lugworms, and oysters. It was shown that the measured RQ/Q ratio correlated with the importance of fumarate reduction in vivo. This is the first demonstration of the role of RQ in eukaryotes, other than parasitic helminths. Furthermore, throughout the development of the liver fluke Fasciola hepatica, a strong correlation was found between the quinone composition and the type of metabolism: the amount of Q was correlated with the use of the aerobic respiratory chain, and the amount of RQ with the use of fumarate reduction. It can be concluded that RQ is an essential component for fumarate reduction in eukaryotes, in contrast to prokaryotes, which use menaquinone in this process. Analyses of enzyme kinetics, as well as the known differences in primary structures of prokaryotic and eukaryotic complexes that reduce fumarate, support the idea that fumarate-reducing eukaryotes possess an enzyme complex for the reduction of fumarate, structurally related to the succinate dehydrogenasetype complex II, but with the functional characteristics of the prokaryotic fumarate reductases.Living with hypoxia or even anoxia is an everyday experience for many organisms. Not only many prokaryotes, but many eukaryotic organisms as well can function (temporarily) without oxygen. Parasitic helminths, freshwater snails, and some lower marine organisms are known to be able to survive anaerobic conditions by adaptation of their energy metabolism. In addition to simple fermentation in which glucose is degraded to ethanol or lactate, most of these facultative anaerobic eukaryotes contain another fermentation variant, malate dismutation (Fig. 1). Malate dismutation is found in both strictly and facultative anaerobically functioning prokaryotes as well as in some eukaryotes that are capable of functioning anaerobically, like parasitic helminths (1), freshwater snails (2), mussels (3), oysters (4), and lugworms and other marine invertebrates (5). Although several variations of malate dismutation with various end products occur, the use of the production of succinate as an electron sink is universal. The reduction of malate to succinate occurs in two reactions that reverse part of the Krebs cycle, and the reduction of fumarate is the essential NADHconsuming reaction to maintain redox balance. There...

show abstract

Section: Resultsmentioning

confidence: 99%