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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