Biochemical similarities and differences between the catalytic [4Fe-4S] cluster containing fumarases FumA and FumB from Escherichia coli.
| Autor: | van Vugt-Lussenburg BM; Department of Biotechnology, Delft University of Technology, Delft, The Netherlands., van der Weel L, Hagen WR, Hagedoorn PL |
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| Jazyk: | angličtina |
| Zdroj: | PloS one [PLoS One] 2013; Vol. 8 (2), pp. e55549. Date of Electronic Publication: 2013 Feb 06. |
| DOI: | 10.1371/journal.pone.0055549 |
| Abstrakt: | Background: The highly homologous [4Fe-4S] containing fumarases FumA and FumB, sharing 90% amino acid sequence identity, from Escherichia coli are differentially regulated, which suggests a difference in their physiological function. The ratio of FumB over FumA expression levels increases by one to two orders of magnitude upon change from aerobic to anaerobic growth conditions. Methodology/principal Findings: To understand this difference in terms of structure-function relations, catalytic and thermodynamic properties were determined for the two enzymes obtained from homologous overexpression systems. FumA and FumB are essentially identical in their Michaelis-Menten kinetics of the reversible fumarate to L-malate conversion; however, FumB has a significantly greater catalytic efficiency for the conversion of D-tartrate to oxaloacetate consistent with the requirement of the fumB gene for growth on D-tartrate. Reduction potentials of the [4Fe-4S](2+) Lewis acid active centre were determined in mediated bulk titrations in the presence of added substrate and were found to be approximately -290 mV for both FumA and FumB. Conclusions/significance: This study contradicts previously published claims that FumA and FumB exhibit different catalytic preferences for the natural substrates L-malate and fumarate. FumA and FumB differ significantly only in the catalytic efficiency for the conversion of D-tartrate, a supposedly non-natural substrate. The reduction potential of the substrate-bound [4Fe-4S] active centre is, contrary to previously reported values, close to the cellular redox potential. |
| Databáze: | MEDLINE |
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