Biological activity of ethanol in relation to its vapour pressure. Note 1:Inactivation of polyphenoloxidase in model systems

The relationship between the inactivation of enzymes by ethanol and its vap our pressure Mas studied in a simple model system containing polyphenoloxid ase (PPO). Thr residual activity of PPO incubated in the temperature range from 15 to 90 degreesC in the presence of increasing amounts of ethanol was evaluated. For each temperature of incubation, the residual activity of PP O as well as its thermal stability decreased as ethanol concentration incre ased PPO activation energy obtained by the Arrhenius model indicated that t he efficiency of ethanol increased as temperature increased. PPO activity n as significantly correlated bl a simple equation with water and ethanol vap our pressure. In addition. PPO inactivation appeared to be strongly affecte d by the vapour pressure of water and/or ethanol. Measures of vapour pressu re were concluded to be suitable for the study of the inactivation effect t owards the enzyme when changes in both concentration and temperature are in volved. (C) 2000 Academic Press.