Polygalacturonase in normal and abnormal tomato fruit

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Abstract
An efficient extraction system for the desorption of polygalacturonase from fruit tissue was developed. Five pectic-acid preparations were compared as substrates for polygalacturonase and the pH-activity relations investigated. Polygalacturonase activity was determined during the ripening of fruit of 2 varieties of tomato. No polygalacturonase activity was found in green fruit; thereafter the activity rose exponentially with time to the orange stage, increasing further to the red stage. Enzyme activity continued to rise as fruit became overripe. The well known physiological disorder, "blotchy" ripening, led to a lowered activity in the apparently normal red area, and to a severe decrease in activity in the abnormal non-red area. The distribution of polygalacturonase in parts of the fruit during ripening was studied. It is concluded that "blotchy" ripening is associated with a failure in the synthesis of polygalacturonase, although it is uncertain whether this lack of the enzyme is a cause or an effect of the disorder.