Kinetic and structural analysis of a new group of acyl-CoA carboxylases found in Streptomyces coelicolor A3(2)
Kinetic and structural analysis of a new group of acyl-CoA carboxylases found in Streptomyces coelicolor A3(2)
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DOI：
10.1074/jbc.m203263200
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发表时间：
2002-08-23
影响因子：
4.8
通讯作者：
Gramajo, H
中科院分区：
文献类型：
--
作者：
Diacovich, L;Peirú, S;Gramajo, H
从天蓝色链霉菌（Streptomycescoelicolor）中分离纯化了两种酰基辅酶A羧化酶，并成功地将其重组。两种复合物共享相同的生物素化α亚基AccA 2。β和β亚基对每个复合物都是特异性的;因此，对于丙酰辅酶A羧化酶复合物，β和β亚基组分是PccB和PccE，而对于乙酰辅酶A羧化酶复合物，组分是AccB和AccE。这两个复合物显示出非常低的活性，在相应的α亚基的情况下，除了PccE或AccE显着增加的酶的比活性。两种酰基辅酶A羧化酶的动力学性质在其底物特异性上显示出明显的差异。乙酰辅酶A羧化酶能够以大致相同的特异性羧化乙酰辅酶A、丙酰辅酶A或丁酰辅酶A。丙酰辅酶A羧化酶不能识别乙酰辅酶A作为底物，而丙酰辅酶A的特异性常数比丁酰辅酶A高2倍。对于这两种酶的α亚基被发现专门与其羧基转移酶的组成部分，形成一个β-α亚复合物相互作用，这似乎有利于进一步相互作用的α组分与这些亚基。已发现的ESTA亚基遗传连锁的几个羧基转移酶的不同的链霉菌属物种，我们建议，这个亚基反映了一个独特的特点，一个新的组酰基辅酶A羧化酶。
Two acyl-CoA carboxylases from Streptomyces coelicolor have been successfully reconstituted from their purified components. Both complexes shared the same biotinylated alpha subunit, AccA2. The beta and the epsilon subunits were specific from each of the complexes; thus, for the propionyl-CoA carboxylase complex the beta and epsilon components are PccB and PccE, whereas for the acetyl-CoA carboxylase complex the components are AccB and AccE. The two complexes showed very low activity in the absence of the corresponding epsilon subunits; addition of PccE or AccE dramatically increased the specific activity of the enzymes. The kinetic properties of the two acyl-CoA carboxylases showed a clear difference in their substrate specificity. The acetyl-CoA carboxylase was able to carboxylate acetyl-, propionyl-, or butyryl-CoA with approximately the same specificity. The propionyl-CoA carboxylase could not recognize acetyl-CoA as a substrate, whereas the specificity constant for propionyl-CoA was 2-fold higher than for butyryl-CoA. For both enzymes the epsilon subunits were found to specifically interact with their carboxyltransferase component forming a beta-epsilon sub-complex; this appears to facilitate the further interaction of these subunits with the alpha component. The epsilon subunit has been found genetically linked to several carboxyltransferases of different Streptomyces species; we propose that this subunit reflects a distinctive characteristic of a new group of acyl-CoA carboxylases.