Proteases from papaya peels were extracted with water followed by precipitation
with ethanol and 57.6% yield was obtained. Their maximum hydrolysis of casein comparing
to proteases from latex were similar in temperature but different in pH. Both of papaya
proteases were fully activated by 5 mM cysteine, the peel enzymes were activated 1.6 times
higher than latex enzymes. The peel proteases are also more stable in pH ≥ 8 and at 80oC than
the latex proteases. Cathodic polyacrylamide gel electrophoresis and in situ proteolysis verified
that papaya peel proteases are composed of papain as a major component, chymopapain,
and possible two proteases which are absent in crude papain. Separation by anodic
polyacrylamide gel electrophoresis and in situ proteolysis illustrated that proteases from papaya
peels contained a protease with pI less than 8.3. Anion-exchange chromatography indicated
that papaya peel proteases consisted of a number of proteins and proteases different from
those found in papaya proteases.