Nogues M, Cuenda A, Henao F, Gutiérrez-Merino C
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
Z Naturforsch C J Biosci. 1996 Jul-Aug;51(7-8):591-8.
The glycogenolytic-sarcoplasmic reticulum complex from rat skeletal muscle accumulates Ca2+ upon stimulation of glycogen phosphorolysis in the absence of added ATP. It is shown that an efficient Ca2+ uptake involves the sequential action of glycogen phosphorylase, phosphoglucomutase and hexokinase, which generate low concentrations of ATP (approximately 1-2 microM) compartmentalized in the immediate vicinity of the sarcoplasmic reticulum Ca2+, Mg(2+)-ATPase (the Ca2+ pump). The Ca2+ uptake supported by glycogenolysis in this subcellular structure is strongly stimulated by micromolar concentrations of AMP, showing that the glycogen phosphorylase associated with this complex is in the dephosphorylated b form. The results point out that the flux through this compartmentalized metabolic pathway should be enhanced in physiological conditions leading to increased AMP concentrations in the sarcoplasm, such as long-lasting contractions and in ischemic muscle.
来自大鼠骨骼肌的糖原分解-肌浆网复合体在无外加ATP的情况下，受糖原磷酸解刺激时会积累Ca2+。结果表明，高效的Ca2+摄取涉及糖原磷酸化酶、磷酸葡萄糖变位酶和己糖激酶的顺序作用，它们在肌浆网Ca2+、Mg(2+)-ATP酶（Ca2+泵）紧邻区域产生低浓度的ATP（约1-2 microM）。该亚细胞结构中糖原分解所支持的Ca2+摄取受到微摩尔浓度AMP的强烈刺激，表明与该复合体相关的糖原磷酸化酶处于去磷酸化的b形式。结果指出，在导致肌浆中AMP浓度增加的生理条件下，如长时间收缩和缺血肌肉中，通过这种区域化代谢途径的通量应会增强。
