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Detoxification of hexavalent chromium by Leucobacter sp. uses a reductase with specificity for dihydrolipoamide
Abhipsa Sarangi,
Published in Wiley-VCH Verlag
2016
PMID: 26377775
Volume: 56
   
Issue: 2
Pages: 175 - 183
Abstract
Leucobacter sp. belongs to the metal stressed community and possesses higher tolerance to metals including chromium and can detoxify toxic hexavalent chromium by reduction to less toxic trivalent chromium. But, the mechanism of reduction of hexavalent chromium by Leucobacter sp. has not been studied. Understanding the enzyme catalyzing reduction of chromium is important to improve the species for application in bioremediation. Hence, a soluble reductase catalyzing the reduction of hexavalent chromium was purified from a Leucobacter sp. and characterized. The pure chromate reductase was obtained from the cell-free extract through hydrophobic interaction and gel filtration column chromatographic methods. It was a monomeric enzyme and showed similar molecular weights in both gel filtration (∼68KDa) and SDS-PAGE (64KDa). It reduced Cr(VI) using both NADH and NADPH as the electron donor, but exhibited higher activity with NADH. The optimal activity was found at pH 5.5 and 30°C. The Km and Vmax for Cr(VI) reduction with NADH were 46.57μM and 0.37μmolmin-1 (mg protein) -1, respectively. The activity was inhibited by p-hydroxy mercury benzoate, Ag2+ and Hg2+ indicating the role of thiol groups in the catalysis. The spectrophotometric analysis of the purified enzyme showed the absence of bound flavin in the enzyme. The N-terminal amino acid sequence and LC/MS analysis of trypsin digested purified enzyme showed similarity to dihydrolipoyl dehydrogenase. The purified enzyme had dihydrolipoyl dehydrogenase activity with dihydrolipoamide as the substrate, which suggested that Leucobacter sp. uses reductase with multiple substrate specificity for reduction of Cr(VI) detoxification. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
About the journal
JournalData powered by TypesetJournal of Basic Microbiology
PublisherData powered by TypesetWiley-VCH Verlag
ISSN0233111X
Open AccessNo
Concepts (34)
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    CHROMATE REDUCTASE
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    Chromium
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    CHROMIUM HEXAVALENT ION
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    Coenzyme
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    DIHYDROLIPOAMIDE
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    Dihydrolipoamide dehydrogenase
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    Enzyme inhibitor
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    Nicotinamide adenine dinucleotide
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    NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE
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    Oxidoreductase
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    THIOCTIC ACID
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    Actinobacteria
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    Analogs and derivatives
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    Biotransformation
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    Chemistry
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    Enzymology
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    Isolation and purification
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    Liquid chromatography
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    Mass spectrometry
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    Metabolism
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    Molecular weight
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    pH
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    Polyacrylamide gel electrophoresis
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    Spectrophotometry
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    Temperature
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    Chromatography, liquid
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    Coenzymes
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    Electrophoresis, polyacrylamide gel
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    Enzyme inhibitors
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    Hydrogen-ion concentration
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    NAD
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    NADP
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    Oxidoreductases
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    THIOCTIC ACID