The endopolygalacturonase secreted by Rhizopus stolonifer Ehr. ex Fr. in vivo during infection of strawberries of the cultivar ‘ Cambridge Favourite’ was extracted with a solution of sodium chloride and partially purified by gel filtration and ion-exchange chromatography. Partial purification removed 99·8 % of the contaminating uronide materials, but the enzyme yield was reduced to 56 % and the specific activity was increased only 2·5 times. The partially purified enzyme exhibited maximum stability at pH 4·0 to 6·0 and optimal activity at pH 4·6 to 4·8.A linear thermal-inactivation pattern between 30 and 50 °C was demonstrated and complete and irreversible inactivation was achieved by heating to 60 °C for 20 min. Enzyme activity was inhibited by 20 % or less by a range of enzyme inhibitors and cations, with 87 % inhibition occurring in the presence of 10−3m-Hg++. The molecular weight of the enzyme was calculated as 60000, and the sedimentation and diffusion data suggested that the enzyme molecule has a high degree of asymmetry.
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