Energization of Bacillus subtilis membrane vesicles increases catalytic activity of succinate: Menaquinone oxidoreductase

In this work, high ΔμH + -dependent succinate oxidase activity has been demonstrated for the first time with membrane vesicles isolated from Bacillus subtilis . The maximal specific rate of succinate oxidation by coupled inside-out membrane vesicles isolated from a B. subtilis strain overproducing s...

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Bibliographic Details
Published in:Biochemistry (Moscow) 2010, Vol.75 (1), p.50-62
Main Authors: Azarkina, N. V., Konstantinov, A. A.
Format: Article
Language:English
Subjects:
Bacillus subtilis - enzymology
Bacteria
Biochemistry
Biomedical and Life Sciences
Biomedicine
Bioorganic Chemistry
Cells
Chlorophenols - chemistry
Electron Transport
Enzymes
Ionophores
Kinetics
Life Sciences
Membranes
Membranes - metabolism
Microbiology
Oxidases
Oxidation
Oxidation-Reduction
Oxidoreductases - chemistry
Oxidoreductases - metabolism
Succinic Acid - metabolism
Thermodynamics
Vitamin K 2 - metabolism
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Summary:In this work, high ΔμH + -dependent succinate oxidase activity has been demonstrated for the first time with membrane vesicles isolated from Bacillus subtilis . The maximal specific rate of succinate oxidation by coupled inside-out membrane vesicles isolated from a B. subtilis strain overproducing succinate:menaquinone oxidoreductase approaches the specific rate observed with the intact cells. Deenergization of the membrane vesicles with ionophores or alamethicin brings about an almost complete inhibition of succinate oxidation. An apparent K m for succinate during the energy-dependent succinate oxidase activity of the vesicles (2.2 mM) is higher by an order of magnitude than the K m value measured for the energy-independent reduction of 2,6-dichlorophenol indophenol. The data reveal critical importance of ΔμH + for maintaining active electron transfer by succinate:menaquinone oxidoreductase. The role of ΔμH + might consist in providing energy for thermodynamically unfavorable menaquinone reduction by succinate by virtue of transmembrane electron transport within the enzyme down the electric field; alternatively, ΔμH + could play a regulatory role by maintaining the electroneutrally operating enzyme in a catalytically active conformation.
ISSN:0006-2979
1608-3040
DOI:10.1134/S0006297910010074