ACTIVATION OF RIBULOSE-1,5-BISPHOSPHATE OXYGENASE - ROLE OF MG2+, CO2, AND PH
ACTIVATION OF RIBULOSE-1,5-BISPHOSPHATE OXYGENASE - ROLE OF MG2+, CO2, AND PH
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DOI：
10.1016/0003-9861(76)90565-8
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发表时间：
1976-01-01
影响因子：
3.9
通讯作者：
LORIMER, GH
中科院分区：
文献类型：
--
作者：
BADGER, MR;LORIMER, GH
核酮糖-1,5-二磷酸加氧酶（来自菠菜叶）通过与 CO2 和 Mg2+ 一起孵育而被激活，并在通过凝胶过滤除去 CO2 和 Mg2+ 后失活。酶的活性取决于预孵育时 CO2 和 Mg2+ 的浓度以及预孵育 pH 值。这表明活化涉及酶-CO2-Mg平衡复合物的可逆形成。活化过程的动力学与 G.H. 所描述的相同。 Lorimer 等人的核酮糖二磷酸羧化酶 [EC 4.1.1.39] 与有序可逆反应序列一致：.**图形**。在恒定浓度的 CO2 和 Mg2+ 下预孵育后，酶的活性随着 pH 值的升高而增加，表明 CO2 与具有碱性 pK 的酶组发生反应。由于CO2和O2在催化位点竞争性地相互作用，CO2和Mg2+对核酮糖二磷酸加氧酶的激活表明参与激活过程的CO2分子与在羧化酶反应过程中固定的CO2分子不同。催化位点的加氧酶和羧化酶功能显然是紧密耦合的而不是彼此独立的。
Ribulose-1,5-bisphosphate oxygenase [from spinach leaves] was activated by incubation with CO2 and Mg2+ and inactivated upon removal of CO2 and Mg2+ by gel filtration. The activity of the enzyme was dependent upon the preincubation concentrations of CO2 and Mg2+ and upon the preincubation pH. This indicated that activation involved the reversible formation of an equilibrium complex of enzyme-CO2-Mg. The kinetics of the activation process were the same as those described by G.H. Lorimer et al., for ribulose bisphosphate carboxylase [EC 4.1.1.39] and are consistent with the ordered reversible reaction sequence: .**GRAPHIC**. The activity of the enzyme, after preincubation at constant concentrations of CO2 and Mg2+, increased as the pH was raised, suggesting that CO2 reacted with an enzyme group having an alkaline pK. Since CO2 and O2 interact competitively at the catalytic site, the activation of ribulose bisphosphate oxygenase by CO2 and Mg2+ indicates that the CO2 molecule which takes part in the activation process is not the same as that which becomes fixed during the carboxylase reaction. The oxygenase and carboxylase functions of the catalytic site apparently are tightly coupled rather than independent of one another.