糖原分解（糖原分解）
中文名称
通路描述
细胞质中的糖原分解在所有组织中通过相同的化学步骤进行，但分别通过组织特异性同工酶和信号通路进行调节，以允许肝脏糖原和其他组织中不同的生理命运。糖原磷酸化酶，可由磷酸化激酶激活，催化从糖原分支末端移除葡萄糖残基，形成葡萄糖 1-磷酸。每个分支的末端四个残基由脱支酶在两步催化下移除，糖原磷酸化酶活动进一步完成糖原分解过程。图显示了磷酸化酶和脱支酶的作用。每个分支的第一个葡萄糖残基释放为游离葡萄糖；所有其他残基释放为葡萄糖 1-磷酸。后者可在与其他途径共享的步骤中转化为葡萄糖 6-磷酸（Villar-Palasi 和 Larner 1970; Hers 1976）。糖原也可被摄取到溶酶体中，在那里它通常由单一酶溶酶体α-葡萄糖苷酶（GAA）分解。肝脏中的酶生成 1,5-二酮基庚糖 -1,5-二磷酸，后者可还原为 1,5-二酮基葡萄糖 -1,5-二醇，这一系列事件可能代表糖原分解的一个新颖次要途径（Kametani 等 1996）。
英文描述
Glycogen breakdown (glycogenolysis) Cytosolic glycogen breakdown occurs via the same chemical steps in all tissues but is separately regulated via tissue specific isozymes and signaling pathways that enable distinct physiological fates for liver glycogen and that in other tissues. Glycogen phosphorylase, which can be activated by phosphorylase kinase, catalyzes the removal of glucose residues as glucose 1-phosphate from the ends of glycogen branches. The final four residues of each branch are removed in two steps catalyzed by debranching enzyme, and further glycogen phosphorylase activity completes the process of glycogen breakdown. The figure shows the actions of phosphorylase and debranching enzyme. The first glucose residue in each branch is released as free glucose; all other residues are released as glucose 1-phosphate. The latter molecule can be converted to glucose 6-phosphate in a step shared with other pathways (Villar-Palasi and Larner 1970; Hers 1976).Glycogen can also be taken up into lysosomes, where it is normally broken done by the action of a single enzyme, lysosomal alpha-glucosidase (GAA).Enzymes in liver generate 1,5-anhydro-D-fructose from glycogen, which in turn can be reduced to 1,5-anhydro-D-glucitol, a sequence of events that may represent a novel minor pathway for glycogen breakdown (Kametani et al. 1996).
所含基因
14 个基因