Carter J, Smith E E
Carbohydr Res. 1978 Mar;61:395-406. doi: 10.1016/s0008-6215(00)84499-7.
The high reactivities exhibited by rabbit-muscle synthase and phosphorylase for unmodified glycogen-acceptors decrease progressively, presumably because of a large increase in apparent Km as the glycogen molecule is converted into its component maltosaccharide chains by the debranching enzyme, isoamylase. Elongation of the outer chains of glycogen acceptor also results in decreased reactivities of the two transglucosylases and this is shown, for phosphorylase acting in the direction of glucan synthesis, to be caused by a decrease in the Vmax of the reaction. A partial restoration of the degradative reactivity of phosphorylase by a limited alpha-amylolysis of the long outer-chains of modified glycogen suggests a role of cytoplasmic alpha-amylase in mammalian glycogen metabolism.
兔肌合成酶和磷酸化酶对未修饰糖原受体表现出的高反应性逐渐降低，推测这是由于随着糖原分子被脱支酶异淀粉酶转化为其组成的麦芽糖链，表观Km大幅增加所致。糖原受体外链的延长也会导致两种转葡萄糖基酶的反应性降低，对于朝着葡聚糖合成方向作用的磷酸化酶而言，这表明反应的Vmax降低是其原因。通过对修饰糖原的长外链进行有限的α-淀粉酶解，部分恢复了磷酸化酶的降解反应性，这表明细胞质α-淀粉酶在哺乳动物糖原代谢中发挥作用。
