A highly thermostable trehalase from the thermophilic bacterium Rhodothermus marinus
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Trehalases play a central role in the metabolism of trehalose and can be found in a wide variety of organisms. A periplasmic trehalase (α,α-trehalose glucohydrolase, EC 184.108.40.206) from the thermophilic bacterium Rhodothermus marinus was purified and the respective encoding gene was identified, cloned and overexpressed in Escherichia coli. The recombinant trehalase is a monomeric protein with a molecular mass of 59 kDa. Maximum activity was observed at 88°C and pH 6.5. The recombinant trehalase exhibited a K m of 0.16 mM and a V max of 81 μmol of trehalose (min)−1 (mg of protein)−1 at the optimal temperature for growth of R. marinus (65°C) and pH 6.5. The enzyme was highly specific for trehalose and was inhibited by glucose with a K i of 7 mM. This is the most thermostable trehalase ever characterized. Moreover, this is the first report on the identification and characterization of a trehalase from a thermophilic bacterium.
KeywordsRhodothermus marinus Periplasmic trehalase Glycosidase Thermostability
This work was funded by the European Commission Contracts QLK3-CT-2000-00640 and COOP-CT-2003-508644 and Fundação para a Ciência e a Tecnologia and FEDER, Portugal, POCI/59310/2004. We thank Winfried Boos, Konstanz, for a fruitful collaboration that led to the discovery of trehalase activity in R. marinus. M. Regalla from Analytical Services performed the N-terminal sequencing at the Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal. C. Jorge acknowledges a PhD grant from PRAXIS XXI (SFRH/BD/10572/2002).
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