| Abstract: | A homogenous endo-polygalacturonase (EC 3.2.1.15,) has been isolated from mature pickling cucumbers. This is the first report of an endo-polygalacturonase in cucumbers. The enzyme was purified by three chromatography steps on Sephadex cation exchangers. The molecular weight is 35,000 daltons. With polygalacturonic acid as the substrate at an ionic strength (μ) of 0.15, the pH optimum is 5.6. The enzyme is not active atμ= 0.027. Maximum activity occurred atμ= 0.2. The half-life of the enzyme is 1.2 min at 70°C in pH 5.2, 0.1 M acetate buffer. An inhibitor, isolated from the sericea lespedeza, which inhibits polygalacturonases from fungal sources, also inhibits the cucumber enzyme. This enzyme may be involved in tissue breakdown during the latter stages of fruit development. |
