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EC 1.3.5.1 Details
EC number
1.3.5.1
Accepted name
succinate dehydrogenase
Reaction
succinate + a quinone = fumarate + a quinol
Other name(s)
succinate dehydrogenase (quinone), succinate dehydrogenase (ubiquinone), succinic dehydrogenase, complex II (ambiguous), succinate dehydrogenase complex, SDH (ambiguous), succinate:ubiquinone oxidoreductase, fumarate reductase (quinol), FRD, menaquinol-fumarate oxidoreductase, succinate dehydrogenase (menaquinone), succinate:menaquinone oxidoreductase, fumarate reductase (menaquinone)
Systematic name
succinate:quinone oxidoreductase
CAS registry number
9028-11-9
Comment
A complex generally comprising an FAD-containing component that also binds the carboxylate substrate (A subunit), a component that contains three different iron-sulfur centers [2Fe-2S], [4Fe-4S], and [3Fe-4S] (B subunit), and a hydrophobic membrane-anchor component (C, or C and D subunits) that is also the site of the interaction with quinones. The enzyme is found in the inner mitochondrial membrane in eukaryotes and the plasma membrane of bacteria and archaea, with the hydrophilic domain extending into the mitochondrial matrix and the cytoplasm, respectively. Under aerobic conditions the enzyme catalyses succinate oxidation, a key step in the citric acid (TCA) cycle, transferring the electrons to quinones in the membrane, thus linking the TCA cycle with the aerobic respiratory chain (where it is known as complex II). Under anaerobic conditions the enzyme functions as a fumarate reductase, transferring electrons from the quinol pool to fumarate, and participating in anaerobic respiration with fumarate as the terminal electron acceptor. The enzyme interacts with the quinone produced by the organism, such as ubiquinone, menaquinone, caldariellaquinone, thermoplasmaquinone, rhodoquinone etc. Some of the enzymes contain two heme subunits in their membrane anchor subunit. These enzymes catalyse an electrogenic reaction and are thus classified as EC 7.1.1.12, succinate dehydrogenase (electrogenic, proton-motive force generating).
History
created 1983 (EC 1.3.99.1 created 1961, incorporated 2014, EC 1.3.5.4 created 2010, incorporated 2022), modified 2022
EC Tree
1.3.99.9 created 1976, deleted 2002