Membrane-bound succinate dehydrogenase of Bacillus pumilus strain 5: effects of modulators of monoelectron transfer.
The membrane-bound succinate dehydrogenase (SDH; EC 1.3.99.1) of Bacillus pumilus strain 5 was investigated as succinate:ferricyanide oxidoreductase activity at 27 degrees C. A Km of 8.3 x 10(-3) M was obtained, and the Vmax was 1.8 x 10(-6) mole succinate dehydrogenated min-1 mg-1 membrane protein, at a substrate (succinate) concentration below 40 x 10(-3) M. Above this succinate concentration the Km was 102 x 10(-3) M and the Vmax was 3.7 x 10(-6) mole succinate min-1 mg-1 membrane protein. Para-benzoquinone or 2,4-dinitrophenylhydrazine, in micromolar amounts inhibited the enzyme by serving as an electron sink. Hydroxyl radical (OH.) scavengers, mannitol and benzoate, activated the enzyme, while superoxide dismutase (SOD) had no effect on the enzyme. Thus, the mechanism of electron transfer from succinate to Fe(CN)3-(6) through SDH does not involve superoxide (O2-) as a rate-limiting intermediate.
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Department of Biochemistry, University of Nigeria, Nsukka.
Okoro
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D001407:Bacillus / Q000201:enzymology*; D001565:Benzoates / Q000494:pharmacology; D016227:Benzoquinones; D004579:Electron Transport; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D005516:Food Microbiology; D007700:Kinetics; D008353:Mannitol / Q000494:pharmacology; D010659:Phenylhydrazines / Q000494:pharmacology; D011809:Quinones / Q000494:pharmacology; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology
D001565:Benzoates; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D010659:Phenylhydrazines; D011809:Quinones; C004787:2,4-dinitrophenylhydrazine; D008353:Mannitol; C004532:quinone; D013482:Superoxide Dismutase; D013385:Succinate Dehydrogenase