Kinetics denaturation of yeast alcohol dehydrogenase and the effect of temperature and trehalose. An isothermal microcalorimetry study

The decrease in biological activity of alcohol dehydrogenase (YADH), due to its spontaneous denaturation, is accompanied by heat exchange of the enzym e solution. The spontaneous denaturation of YADH in 50 mM phosphate buffer, pH 7.8, at two temperatures of 27 degrees and 37 degrees C has been invest igated by monitoring the heat exchange and residual activity of an enzyme s olution with respect to time. The kinetics of denaturation was found to obe y a first order law, depending on the concentration of YADH. The rate const ants of denaturation were found to be 0.073 and 0.126 h(-1) at two temperat ures of 27 degrees and 37 degrees C, respectively. These values decreased t o 0.021 and 0.034 h(-1), respectively, in the presence of 1 M trehalose. Mo reover, thermal denaturation study of YADH showed that trehalose leads to t hermal stability enhancement. (C) 1999 Elsevier Science B.V. All rights res erved.