Rauch B, Chak D V, Hasselbach W
Z Naturforsch C Biosci. 1977 Sep-Oct;32(9-10):828-34. doi: 10.1515/znc-1977-9-1027.
The calcium transport protein of the sarcoplasmic reticulum accepts inorganic phosphate rapidly when phosphorylation is initiated either by the addition of phosphate or magnesium ions to the calcium free protein. Phosphorylation proceeds much more slowly when it is initiated by the addition of the calcium chelatro ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) to the phosphate and magnesium containing assay. The time course of phosphorylation following immediately calcium removal is monophasic at all temperatures between 20 degrees and 37 degrees C. In contrast, biphasic time course doses not only apply to net formation of phosphoprotein but also to its exchange with medium phosphate. On addition of calcium, the phosphoprotein decays in a biphasic process the time constants of which are much longer than those observed for phosphoprotein formation. The temperature dependence of the rate as well as of the extent of phosphoprotein formation indicate a discontinuity in the reactivity of the protein.
肌浆网的钙转运蛋白在向无钙蛋白中添加磷酸盐或镁离子引发磷酸化时，会迅速接受无机磷酸盐。当通过向含磷酸盐和镁的测定体系中添加钙螯合剂乙二醇双（β-氨基乙基醚）-N,N'-四乙酸（EGTA）来引发磷酸化时，磷酸化进程要慢得多。在20摄氏度至37摄氏度之间的所有温度下，紧接着钙去除后的磷酸化时间进程都是单相的。相比之下，双相时间进程不仅适用于磷蛋白的净形成，也适用于其与培养基磷酸盐的交换。添加钙后，磷蛋白以双相过程衰减，其时间常数比磷蛋白形成时观察到的长得多。磷蛋白形成速率和程度对温度的依赖性表明该蛋白的反应性存在不连续性。
