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. 1984 May;75(1):21–25. doi: 10.1104/pp.75.1.21

Possible Roles of Calcium and Calmodulin in the Biosynthesis and Secretion of α-Amylase in Rice Seed Scutellar Epithelium 1

Toshiaki Mitsui 1, John T Christeller 1,2, Ikuko Hara-Nishimura 1, Takashi Akazawa 1
PMCID: PMC1066827  PMID: 16663573

Abstract

The scutellar epithelial cells of rice (Oryza sativa L. cv Kimmazé) seeds actively secrete α-amylase in an early stage of germination. Employing an in vivo system of freshly dissected scutellar tissues, effect of Ca2+ on the biosynthesis and the secretion of α-amylase have been studied. The maximum biosynthetic rate was saturated at about 0.5 mm external Ca2+ concentrations, whereas the secretion continued to increase to concentrations above 10 mm Ca2+. In the presence of 1 mm Ca2+, 0.01 μm A-23187 significantly increased both the biosynthesis and the secretion of α-amylase.

A cation-specific requirement for Ca2+ was apparent, since both biosynthesis and extracellular secretion of α-amylase were inhibited by 0.1 mm EGTA but were increased above basal rate only with Ca2+ and Sr2+; K+, Mg2+, and Ba2+ being ineffective.

La3+ and ruthenium red (selective inhibitors of [Ca2+ + Mg2+]-ATPase) were found to profoundly inhibit the secretion of α-amylase. A calmodulin antagonist, W-7, also inhibited the secretion of α-amylase at concentrations where the enzyme synthesis was not much affected. Overall data indicate that Ca2+ movement and secretion of α-amylase are tightly linked and it is likely that they are regulated by the cytoplasmic Ca2+ concentration under possible control by calmodulin.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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