Schumaker K S, Sze H
J Biol Chem. 1987 Mar 25;262(9):3944-6.
In plant cells, transient changes in cytoplasmic Ca2+ levels can modulate numerous developmental processes. Ca2+ is accumulated in the vacuole via a H+/Ca2+ antiport system that is energized by the tonoplast H+-pumping ATPase. Inositol 1,4,5-triphosphate (InsP3), but not inositol 1,4-bisphosphate, myo-inositol 1-phosphate, or fructose 2,6-bisphosphate, caused a transient reduction of Ca2+ levels in tonoplast vesicles. The decrease was dependent on InsP3 concentration (Km apparent = 0.6 microM). The InsP3-induced Ca2+ release was blocked by the Ca2+ antagonist, 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate-HCl. These results suggest that the vacuolar membrane is one target site for InsP3 action and that InsP3 may operate as a second messenger in the mobilization of intracellular Ca2+ in plant cells.
在植物细胞中，细胞质Ca2+水平的瞬时变化可调节众多发育过程。Ca2+通过由液泡膜H+泵ATP酶供能的H+/Ca2+反向转运系统积累在液泡中。肌醇1,4,5-三磷酸（InsP3），而非肌醇1,4-二磷酸、肌醇1-磷酸或果糖2,6-二磷酸，可引起液泡膜小泡中Ca2+水平的瞬时降低。这种降低依赖于InsP3浓度（表观Km = 0.6 microM）。InsP3诱导的Ca2+释放被Ca2+拮抗剂8-(N,N-二乙氨基)-辛基3,4,5-三甲氧基苯甲酸盐酸盐阻断。这些结果表明液泡膜是InsP3作用的一个靶位点，并且InsP3可能作为植物细胞中细胞内Ca2+动员的第二信使发挥作用。
