Lefebvre D D, Duff S M, Fife C A, Julien-Inalsingh C, Plaxton W C
Department of Biology, Queen's University, Kingston, Ontario K7L 3N6 Canada.
Plant Physiol. 1990 Jun;93(2):504-11. doi: 10.1104/pp.93.2.504.
Suspension cells of Brassica nigra responded to Pi deprivation by increasing their potential for Pi influx and by raising the active levels of intracellular, cell surface, and secreted acid phosphatases. These responses, however, were temporally distinct. Phosphate influx capacity increased 15-fold in parallel to a 10-fold decrease in endogenous Pi during 7 days of culture in basal growth medium. In contrast, intracellular and cell surface phosphatase activities changed only after alterations in cellular phosphorus status had been in place for a number of days. Even in nutrient sufficient cells the secretion of phosphatase remained relatively high as did the activities of the other phosphatases. The cell surface acid phosphatase had a K(m) of approximately 10 times that of the influx process and molybdate was a much stronger inhibitor of this phosphatase activity. From these results it appears that Pi absorption and the production or activation of phosphatases are regulated in a distinct manner. In addition, Pi uptake into Brassica nigra cells does not appear to directly involve the cell surface phosphatase under Pi-deficient conditions.
黑芥悬浮细胞对磷缺乏的响应是通过增加其磷流入潜力以及提高细胞内、细胞表面和分泌型酸性磷酸酶的活性水平来实现的。然而，这些响应在时间上是不同的。在基础生长培养基中培养7天期间，磷流入能力增加了15倍，与此同时内源性磷减少了10倍。相比之下，细胞内和细胞表面磷酸酶的活性仅在细胞磷状态改变数天后才发生变化。即使在营养充足的细胞中，磷酸酶的分泌也保持相对较高水平，其他磷酸酶的活性也是如此。细胞表面酸性磷酸酶的K(m)约为磷流入过程的10倍，钼酸盐对这种磷酸酶活性的抑制作用更强。从这些结果来看，磷的吸收以及磷酸酶的产生或激活是以不同的方式进行调节的。此外，在缺磷条件下，磷进入黑芥细胞似乎并不直接涉及细胞表面磷酸酶。
