Abstract
Abstract Tomatoes (Lycopersicon esculentum Mill. ‘Tropic’) were examined for changes during ripening in fruit firmness, water-soluble pectin, the 2 polygalacturonases (PG I and PG II), and polygalacturonase converter. The loss of fruit firmness and increase in water-soluble pectin at the turning stage of ripeness coincided with the appearance of PG activity. The initial activity was due exclusively to PG I, which continued to increase during ripening. PG I was the major polygalacturonase isoenzyme in extracts of tomatoes at all stages of ripeness, contrary to previous reports. PG II was first detected in pink fruit and increased markedly with ripening. Polygalacturonase converter was present in green tomatoes, but also began to increase at the turning stage. The results indicate that PG I may be formed during extraction of tomatoes from PG II and the converter as they are solubilized.
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