In order to quest new potential plant protease and make it industrially
applicable and cost-effective, three novel proteases were detected in tomato
(Lycopersicum esculentum Mill.) fruit by sodium dodecyl sulfate (SDS)–
gelatin–polyacrylamide gel electrophoresis. All three proteases were isolated
and partially purified by heat treatment (70C, 5 min) and ethanol precipitation
(0–33%, v/v), with ninefold increase in specific activity and 31.6% recovery.
These proteases exhibited the highest specificity for gelatin substrate and were
indentified as serine protease. The optimum pH and temperature of proteolytic
activity were pH 8–10 and 37–60C, respectively. They were stable at high pH
(up to 12) and temperature (up to 70C) and in the presence of 20 mM metal
ions (Na+, Ba2+, Ca2+, Mg2+, Mn2+), surfactants (SDS and 80 mM Triton X-100)
and denaturants (urea and dithiothreitol). These results suggested that proteases
from tomato fruit had potential application in food, detergent, tannery
and medical industries.jfbc_