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

Seasonal changes in some hemicellulose-degrading enzymes inJapanese pear fruit were studied in connection with fruit development,softening and over-ripening. These enzyme activities per fruitfresh weight were very high during the cell division and preenlargementstages, and greatly decreased in the enlargement stage. Thereafter,they again exhibited clear increase with ripening. These enzymeactivities per cell (DNA content basis), however, were roughlyconstant throughout the cell division, pre-enlargement and enlargementstages. These cell wall degrading enzymes were divided intothe following three groups by their alteration patterns withripening, i.e. the first group including polygalacturonase,exocellulase and mannanase which seems to be associated withfruit softening, the second one including arabanase, ß-glucosidaseand endocellulase and the third one including xylanase, ß-xylosidaseand ß-galactosidase, both of which seem to functionin cellular breakdown with over-ripening. ¹ This paper is contribution A-87, Fruit Tree Research Station. (Received August 4, 1978; )