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Proteases from papaya latex were partially purified by ammonium sulfate precipitation and separated into two fractions (Fraction I and II ) by carboxymethyl cellelose column chromatography. Each fraction, mixture of the two fractions, and crude extract of the papaya latex at pH 7.0 were inactivated at the range of 60∼90℃ and thermal properties of the enzymes were investigated. In the thermal inactivation of fraction I, the enthalpy of activation was 89.5 kJ/㏖; the entropy of activation, -44.0 J/㏖·K; the free energy of activation, 104.6 kJ/㏖; z-value, 25℃. For fraction II, the enthalpy of activation was 96.5 kJ,/㏖; the entropy of activation, -22.0 J/㏖·K; the free energy of activation, 104.0 kJ/㏖; z-value, 23℃. For the mixture of fraction I and II, the enthalpy of activation was 90.9 kJ/㏖; the entropy of activation, -38.8 J/㏖·K; the free energj of activation, 104.2 kJ/㏖; z-value, 24.6℃. For crude extract, the enthalpy of activation was 11.8 kJ/㏖; the entropy of activation, 22.0 J/㏖·K; the free energy of activation, 106.2 kJ/㏖; z-value, 23.2℃. It was indicated that the fraction I was more heat-stable than the fraction II and this suggested that the thermal stability of the proteases in papaya latex is probably due to the fraction I.
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