The activity and conformation changes of catalase in water-ethanol mixtures were measured at 298.15K by means of microcalorimetry and fluorescence spectroscopy. The results showed that the Michaelis constant K~m of catalase catalyzed reaction as well as the relative fluorescence intensity of catalase increased the rate constant k~2 and the activity of catalase decreased with increasing the ethanol concentration. The conformation of catalase was changed with losing activity at the various concentration of ethanol. The lose of activity of catalase in water-ethanol mixtures was caused by the inhibition of ethanol and the conformational change of catalase.

Key words: WATER, ETHANOL, CATALASE, CONFORMATION, CATALYTIC ACTIVITY