Heymann E, Junge W
Eur J Biochem. 1979 Apr;95(3):509-18. doi: 10.1111/j.1432-1033.1979.tb12991.x.
Three different subunits of highly purified pig liver esterase (EC 3.1.1.1) can be separated by analytical dodecyl sulfate electrophoresis, though their relative mobilities are very similar. The same subunit bands are obtained with microsomes, in which the esterases have been labeled with the specific active-site-directed inhibitor bis(4-nitro-[14C]phenyl)phosphate. The heterogeneity of the native trimeric enzyme is much more complex, as is demonstrated by isoelectric focussing and polyacrylamide gel electrophoresis. Fractions of esterase which were partially separated by preparative isoelectric focussing show differences in their subunit composition, their amino acid analyses, their tryptic peptide maps, and their C-terminal amino acids. From these experiments various features of the differing esterase subunits can be deduced. Based on the chemical results and on various experiments which did not indicate any secondary modification of the protein side-chains, the molecular basis of the esterase heterogeneity is discussed. We conclude that the native trimeric esterase is a mixture of numerous hybrids of at least three protein subunits with differing but closely related primary sequences. A comparison of the relative specificity of various preparations of pig liver microsomes indicates that genetic differences concerning the composition of liver esterase exist between individuals.
通过分析型十二烷基硫酸钠电泳可分离出高度纯化的猪肝酯酶（EC 3.1.1.1）的三种不同亚基，尽管它们的相对迁移率非常相似。用微粒体也能得到相同的亚基带，其中酯酶已用特异性活性位点导向抑制剂双（4-硝基-[14C]苯基）磷酸酯进行了标记。天然三聚体酶的异质性要复杂得多，等电聚焦和聚丙烯酰胺凝胶电泳证明了这一点。通过制备性等电聚焦部分分离得到的酯酶组分在亚基组成、氨基酸分析、胰蛋白酶肽图和C端氨基酸方面存在差异。从这些实验中可以推断出不同酯酶亚基的各种特征。基于化学结果以及未表明蛋白质侧链有任何二级修饰的各种实验，讨论了酯酶异质性的分子基础。我们得出结论，天然三聚体酯酶是至少三种具有不同但密切相关一级序列的蛋白质亚基的众多杂合体的混合物。对各种猪肝微粒体制剂相对特异性的比较表明，个体之间存在与肝酯酶组成有关的遗传差异。
