Increased Stability and Catalytic Efficiency of Yeast Hexokinase Upon Interaction with Zwitterionic Micelles. Kinetics and Conformational Studies |
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Authors: | Rodrigo Guerra M Lucia Bianconi |
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Institution: | (1) Departamento de Bioquímica Médica, ICB/CCS, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, CEP 21941-590, Brazil;(2) Departamento de Bioquímica Médica, ICB/UFRJ, Prédio do CCS, bloco E, sala 38, Ilha do Fundão, Rio de Janeiro, RJ, CEP 21941-590, Brazil |
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Abstract: | The effect of ligands (glucose, ATP and Mg2+) and zwitterionic micellesof lysophosphatidylcholine (LPC) or N-hexadecyl-N,N-dimethyl-3-ammoniumpropanesulfonate (HPS) in the yeast hexokinase (HK) stability was studied at35°C. The thermal inactivation kinetics followed one-exponentialdecay. The effect of ligands on protecting the enzyme against inactivationfollowed the order: glucose>glucose/Mg2+>ATP/Mg2+ Mg2+ bufferonly. Both LPC and HPS micelles increased the enzyme stability only whenthe incubation medium contained glucose or glucose/Mg2+,suggesting that the protein conformation is a key prerequisite for theenzyme-micelle interaction to take place. This enzyme-micelle interactionresulted in an increased catalytic efficiency (with a decrease in Km forATP and increase in Vmax as well as in changes on the tertiary (intrinsicfluorescence) structure of the yeast hexokinase. |
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Keywords: | Yeast hexokinase Stability Enzyme-micelle interaction Fluorescence Zwitterionic micelle |
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