Alkaline-Induced Unfolding and Salt-induced Folding of Pig Heart Lactate Dehydrogenase Under High pH Conditions

摘要

The alkaline-induced unfolding and the salt-induced folding of pig heart lactate dehydrogenase under high pH conditions have been followed by fluorescence emission spectra and circular dichroic spectra. The results for alkaline-induced denaturation of lactate dehydrogenase show that at low ionic strength, increasing the pH value increased the extent of unfolding of the enzyme to the maximum ultimate unfolded conformation at about pH 13.0. At pH 12.5, although the enzyme was completely inactivated, most of the ordered structure was retained. Even at pH 13.5, the apparently fully unfolded enzyme still retains some ordered secondary structure. Kinetic analysis shows that at high pH, the inactivation rate constants of the enzyme are an order of magnitude faster than the unfolding rate constant at least.