Changes in hemicellulose-degrading enzymes during development and ripening of Japanese pear fruit1

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Abstract
Seasonal changes in some hemicellulose-degrading enzymes in Japanese pear fruit were studied in connection with fruit development, softening and over-ripening. These enzyme activities per fruit fresh weight were very high during the cell division and preenlargement stages, and greatly decreased in the enlargement stage. Thereafter, they again exhibited clear increase with ripening. These enzyme activities per cell (DNA content basis), however, were roughly constant throughout the cell division, pre-enlargement and enlargement stages. These cell wall degrading enzymes were divided into the following three groups by their alteration patterns with ripening, i.e. the first group including polygalacturonase, exocellulase and mannanase which seems to be associated with fruit softening, the second one including arabanase, β-glucosidase and endocellulase and the third one including xylanase, β-xylosidase and β-galactosidase, both of which seem to function in cellular breakdown with over-ripening.