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Changes in the phosphorylation state of sucrose synthase during development of Japanese pear fruit
Author(s) -
Tanase Koji,
Shiratake Katsuhiro,
Mori Hitoshi,
Yamaki Shohei
Publication year - 2002
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1046/j.0031-9317.2001.10137.x
Subject(s) - phosphorylation , pear , sucrose , phosphatase , isozyme , protein phosphorylation , biochemistry , enzyme , gene isoform , sucrose phosphate synthase , chemistry , biology , sucrose synthase , botany , protein kinase a , gene , invertase
Changes in the protein level and phosphorylation state of sucrose synthase (SS) were studied throughout the development of Japanese pear fruit. The level of SS protein was high at the young stage, dropped with fruit enlargement and increased again with fruit maturation. Antibody against phospho‐Ser reacted with SS from young fruit, but did not react with SS that had been dephosphorylated by alkaline phosphatase (AP). The activities of SS isozymes were separated by ion‐exchange chromatography. It was found that the fluctuation in SS activity was caused by two SS isozymes (SSI and SSII); (SSI reacted with antibody against phospho‐Ser, while SSII did not. Phosphorylation of SS affected its kinetic parameters, that is, the affinity of phosphorylated SS for UDP was higher than that of dephosphorylated SS, while it was the contrary for UDP‐glucose. The reaction of dephosphorylated SS was inclined toward sucrose synthesis more than that of phosphorylated SS. Phosphorylated SS protein was most abundant in young fruit, but decreased with fruit development, while non‐phosphorylated SS protein increased in mature fruit. These results suggest that SS isoforms may be affected by post‐translational modifications such as phosphorylation, and that the regulation of phosphorylation may potentially control the properties and functions of SS throughout the development of Japanese pear fruit.