Plant Physiology 82:880-884 (1986)
© 1986 American Society of Plant Biologists
Articles
Preferential Secretion of R-Type  -Amylase Molecules in Rice Seed Scutellum at High Temperatures 1
Toshiaki Mitsui2 and
Takashi Akazawa
Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Chikusa, Nagoya 464, Japan
Exposure of fresh scutella excised from 4-day-old rice seedlings to higher temperatures, (40-42°C), drastically reduced the biosynthesis of  -amylase as determined by the incorporation of [35S]methionine into the immunoprecipitable product. However, the intracellular transport and extracellular secretion of the enzyme molecules were enhanced at high temperatures, indicating that the biosynthesis and secretion of -amylase are distinguishable in their temperature dependency. At the higher temperature regime ( 40°C), the complex-type -amylase isoform, resistant to hydrolytic digestion by endo- -N-acetylglucosaminidase H (Endo--H) was predominantly secreted, whereas at lower temperatures ( 15°C), the isoform susceptible to Endo--H attack was the major molecular form secreted.
2 Holder of Fellowship of the Japan Society for the Promotion of Science for Japanese Junior Scientists, 1986,4-1986,6. Present Address: Department of Agricultural Chemistry, Faculty of Agriculture, Niigata University, Niigata 950-21, Japan.
1 This is paper No. 21 in the series "Enzymic Mechanism of Starch Breakdown in Germinating Rice Seeds." The research was financially aided by grants from the Japanese Ministry of Education (Mombusho) and Mitsubishi Foundation (Tokyo).
|
|
