Meglasson M D, Burch P T, Berner D K, Najafi H, Matschinsky F M
Diabetes. 1986 Oct;35(10):1163-73. doi: 10.2337/diab.35.10.1163.
Alloxan inactivated glucokinase in intact, isolated pancreatic islets incubated in vitro. Inactivation of glucokinase was antagonized by 30 mM glucose present during incubation of islets with alloxan. Glucokinase partially purified from transplantable insulinomas or rat liver was inactivated by alloxan with a half-maximal effect at 2-4 microM alloxan. Inactivation of purified glucokinase was antagonized by glucose, mannose, and 2-deoxyglucose in order of decreasing potency but not by 3-O-methylglucose. Glucose anomers at 6 and 14 mM were discriminated as protecting agents, with the alpha-anomer more effective than the beta-anomer. Glucokinase was not protected from alloxan inactivation by N-acetylglucosamine, indicating that the reactive site for alloxan is not the active site; therefore, glucose may protect glucokinase by inducing a conformational change. Glucokinase is thought to be the glucose sensor of the pancreatic beta-cell. The finding that glucokinase is inactivated by alloxan and protected by glucose with discrimination of its anomers similar to inhibition of glucose-stimulated insulin secretion by alloxan supports this hypothesis and appears to explain the mechanism for inhibition of hexose-stimulated insulin secretion by this agent and the unique role of glucose and mannose as protecting agents.
在体外培养的完整、分离的胰岛中，四氧嘧啶使葡萄糖激酶失活。在胰岛与四氧嘧啶共同孵育期间，30 mM葡萄糖可拮抗葡萄糖激酶的失活。从可移植胰岛素瘤或大鼠肝脏中部分纯化得到的葡萄糖激酶，在2 - 4 microM四氧嘧啶作用下会被其失活，且半数最大效应出现于此浓度范围。纯化后的葡萄糖激酶失活可被葡萄糖、甘露糖和2 - 脱氧葡萄糖按效力递减顺序拮抗，但不能被3 - O - 甲基葡萄糖拮抗。6 mM和14 mM的葡萄糖异头物作为保护剂时可被区分，其中α - 异头物比β - 异头物更有效。N - 乙酰葡糖胺不能保护葡萄糖激酶免于四氧嘧啶失活，这表明四氧嘧啶的反应位点不是活性位点；因此，葡萄糖可能通过诱导构象变化来保护葡萄糖激酶。葡萄糖激酶被认为是胰腺β细胞的葡萄糖传感器。葡萄糖激酶被四氧嘧啶失活且被葡萄糖保护，同时对其异头物的区分类似于四氧嘧啶对葡萄糖刺激的胰岛素分泌的抑制作用，这一发现支持了该假说，并且似乎解释了该试剂抑制己糖刺激的胰岛素分泌的机制以及葡萄糖和甘露糖作为保护剂的独特作用。
