STUDIES ON ATP CITRATE LYASE OF RAT LIVER .4. ROLE OF COA
STUDIES ON ATP CITRATE LYASE OF RAT LIVER .4. ROLE OF COA
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DOI：
10.1093/oxfordjournals.jbchem.a129093
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发表时间：
1969-01-01
影响因子：
2.7
通讯作者：
TAKEDA, Y
中科院分区：
文献类型：
--
作者：
INOUE, H;TSUNEMI, T;TAKEDA, Y
详细介绍了ATP柠檬酸裂解酶[EC 4. 1.3.8]，特别是对CoA的作用方式，使用来自大鼠肝脏的单一均匀制剂进行了研究。结果表明：（1）该酶能快速催化乙酰辅酶A-辅酶A交换，但不能催化乙酰辅酶A-乙酸交换。（2）14 C-乙酸与蛋白质的结合发生在14 C-乙酰辅酶A与酶孵育时，表明形成了酶-乙酸复合物。当通过凝胶过滤分离该复合物，然后与草酰乙酸一起孵育时，形成14 C-柠檬酸盐。未检测到酶-草酰乙酸复合物的形成。（3）该酶容易与游离CoA或在酶-乙酸盐复合物形成期间从乙酰-CoA释放的CoA结合。CoA与酶的结合不取决于添加的ATP的存在，并且结合的CoA可以与外源性CoA自由交换。这些数据表明，酶和CoA之间的联系是不是能量丰富，不像酶和acetate之间的联系。从这些发现中，它的结论是，酶的β-CoA，β-CoA，酶的β-柠檬酸β-CoA和酶的β-acetate β-CoA参与的反应中作为中间体，并排除了柠檬酰CoA作为反应中间体参与的可能性。CoA的额外的作用，除了乙酰受体，也进行了讨论。
The details of the reaction mechanism of ATP citrate lyase [EC 4. 1.3.8], especially on the mode of action of CoA, were investigated using a single homogeneous preparation from rat liver. The results obtained are: ( 1 ) The enzyme rapidly catalyzes the acetyl-CoA— CoA exchange, but not the acetyl-CoA— acetate exchange. ( 2 ) The combination of14C-acetate to the protein occurs on incubation of14C-acetyl-CoA with the enzyme, showing the formation of an enzyme-acetate complex. When this complex is isolated by gel filtration and then incubated with oxaloacetate,14C-citrate is formed. The formation of an enzyme-oxaloacetate complex is not detected. (3 ) The enzyme easily combines with free CoA or CoA that is released from acetyl-CoA during the formation of the enzyme-acetate complex. This binding of CoA to the enzyme does not depend on the presence of added ATP, and the bound CoA is freely exchangeable with exogenous CoA. These data indicate that the linkage between enzyme and CoA is not energy-rich, unlike that between enzyme and acetate.From these findings, it is concluded that enzyme∼P,⋈COA, enzyme∼citrate⋈COAand enzyme∼acetate⋈COAare involved as intermediates in the reaction, and the possibility of an involvement of citryl-CoA as a reaction intermediate is excluded.An additional role of CoA, besides that of an acetyl acceptor, is also discussed.