The effect of aqueous methanol cryosolvents on the heat- and cold-induced denaturation of lactate dehydrogenase.

Abstract

The effect on the low-temperature-induced denaturation temperature of various concentrations of methanol has been studied for lactate dehydrogenase. The results have been compared to similar data for the thermal denaturation temperature. Extrapolations of the low-temperature data show that, in a physiological buffer in the absence of methanol, the cold denaturation temperature would be -30 degrees C. Data obtained with high concentrations of methanol indicate that residues are exposed to a similar degree upon either heat- or cold-induced denaturation. Aggregation does not occur in the cold-denatured protein. Cold-induced denaturation is fully reversible at a protein concentration of 250 micrograms/ml. The spectra of the two denatured forms are similar.