In vitro activation of a galactosyl transferase involved in the osmotic regulation of ochromonas |
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Authors: | Kauss H Quader H |
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Institution: | University of Kaiserslautern, Department of Biology, Postfach 3049, 675 Kaiserslautern, Germany. |
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Abstract: | Osmotic regulation in the flagellate Ochromonas malhamensis Pringsheim is mainly mediated by fluctuations in the pool size of α-galactosyl-(1→1)-glycerol (isofloridoside). A regulated key enzyme of isofloridoside metabolism is the galactosyl transferase producing isofloridoside phosphate. The activity of this enzyme in crude extracts can be increased 5- to 20-fold by incubation at pH 6. The activation occurs in a reaction with a Q10 of 1.5 to 3 and is dependent on time and pH value. Inactivation of the activated form of the enzyme is also time-dependent, and is minimal at the pH value at which activation is optimal. The data suggest a regulation of the enzyme by chemical modification due to the action of auxiliary enzymes. |
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