Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Chikusa, Nagoya 464, Japan.
Plant Physiol. 1984 May;75(1):21-5. doi: 10.1104/pp.75.1.21.
The scutellar epithelial cells of rice (Oryza sativa L. cv Kimmazé) seeds actively secrete alpha-amylase in an early stage of germination. Employing an in vivo system of freshly dissected scutellar tissues, effect of Ca(2+) on the biosynthesis and the secretion of alpha-amylase have been studied. The maximum biosynthetic rate was saturated at about 0.5 mm external Ca(2+) concentrations, whereas the secretion continued to increase to concentrations above 10 mm Ca(2+). In the presence of 1 mm Ca(2+), 0.01 mum A-23187 significantly increased both the biosynthesis and the secretion of alpha-amylase.A cation-specific requirement for Ca(2+) was apparent, since both biosynthesis and extracellular secretion of alpha-amylase were inhibited by 0.1 mm EGTA but were increased above basal rate only with Ca(2+) and Sr(2+); K(+), Mg(2+), and Ba(2+) being ineffective.La(3+) and ruthenium red (selective inhibitors of [Ca(2+) + Mg(2+)]-ATPase) were found to profoundly inhibit the secretion of alpha-amylase. A calmodulin antagonist, W-7, also inhibited the secretion of alpha-amylase at concentrations where the enzyme synthesis was not much affected. Overall data indicate that Ca(2+) movement and secretion of alpha-amylase are tightly linked and it is likely that they are regulated by the cytoplasmic Ca(2+) concentration under possible control by calmodulin.
水稻（Oryza sativa L. cv Kimmazé）种子的盾片上皮细胞在萌发的早期阶段会积极分泌α-淀粉酶。采用新鲜解剖的盾片组织的体内系统，研究了 Ca(2+) 对α-淀粉酶生物合成和分泌的影响。最大生物合成速率在约 0.5 mM 外部 Ca(2+) 浓度下达到饱和，而分泌则继续增加到超过 10 mM Ca(2+) 的浓度。在 1 mM Ca(2+) 存在下，0.01 mum A-23187 显著增加了α-淀粉酶的生物合成和分泌。Ca(2+) 的阳离子特异性需求是明显的，因为α-淀粉酶的生物合成和细胞外分泌都被 0.1 mM EGTA 抑制，但仅在 Ca(2+) 和 Sr(2+) 存在下才高于基础速率；K(+)、Mg(2+) 和 Ba(2+) 无效。La(3+) 和钌红（[Ca(2+) + Mg(2+)]-ATP 酶的选择性抑制剂）被发现可深度抑制α-淀粉酶的分泌。钙调蛋白拮抗剂 W-7 也在对酶合成影响不大的浓度下抑制α-淀粉酶的分泌。总体数据表明，Ca(2+) 运动和α-淀粉酶的分泌紧密相关，并且它们可能受到细胞质 Ca(2+) 浓度的调节，可能受钙调蛋白的控制。
