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Biosynthesis and function of trehalose inEctothiorhodospira halochloris
Authors:Karin Lippert  Erwin A Galinski  Hans G Trüper
Institution:(1) Institut für Mikrobiologie & Biotechnologie, der Universität Bonn, Meckenheimer Allee 168, 5300 Bonn, Germany
Abstract:Trehalose-6-phosphate synthase, catalyzing the reaction between UDP-glucose and glucose 6-phosphate and forming trehalose 6-phosphate, was isolated and partially purified (30-fold) from the phototrophic, haloalkaliphilic bacteriumEctothiorhodospira halochloris. The activity is stabilized by 20mM MgCl2, 50mM NaCe and 2M glycine betaine. The molecular weight was 63000.The enriched enzyme had a MgCl2 optimum at 3–6mM, a pH optimum at 7.5 (in Tris-HCl buffer) and a temperature optimum at 50°C. The Km-values were 1.5×10–3M for UDP-glucose and 2×10–3M for glucose 6-phosphate. The enzyme showed a salinity dependence with optimal concentrations between 100 and 300mM salt. Higher concentrations of salt resulted in a decrease in activity. In the presence of inhibitory salt concentrations the compatible solute glycine betaine had a protective effect with a maximum between 0.5 and 2.0M.
Keywords:Ectothiorhodospira halochloris  glycine betaine  salt protection  trehalose
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