Nucci R, Raia C A, Vaccaro C, Rossi M, Whitehead E P
C.N.R., Institute of Protein Biochemistry and Enzymology, Napoli, Italy.
Arch Biochem Biophys. 1991 Aug 15;289(1):19-25. doi: 10.1016/0003-9861(91)90436-m.
The hexameric allosteric enzyme deoxycytidylate aminohydrolase from donkey spleen is shown by equilibrium dialysis to bind specifically the allosteric inhibitor, dTTP, the activator dCTP, and the substrate analog dAMP each at six sites (the dTTP and dCTP sites may or may not be identical). These conclusions contrast with earlier ones that there were four sites for each effector; reasons for the discrepancy are discussed. With the knowledge of site numbers and the kinetic information from the accompanying paper it is concluded that the kinetic cooperativity of the enzyme excludes a concerted conformational transition mechanism. Amino acid analysis gives a molecular weight of 18,842 Da per subunit, i.e., 113,052 for the hexamer. A new simplified purification of homogeneous enzyme from donkey spleen probably useful for dCMP aminohydrolase from other sources is described.
通过平衡透析表明，来自驴脾脏的六聚体变构酶脱氧胞苷酸氨基水解酶在六个位点特异性结合变构抑制剂dTTP、激活剂dCTP和底物类似物dAMP（dTTP和dCTP位点可能相同也可能不同）。这些结论与早期认为每个效应物有四个位点的结论不同；讨论了差异的原因。根据位点数量的知识和随附论文中的动力学信息，得出该酶的动力学协同性排除了协同构象转变机制的结论。氨基酸分析得出每个亚基的分子量为18,842 Da，即六聚体的分子量为113,052 Da。描述了一种从驴脾脏中纯化同质酶的新的简化方法，该方法可能对从其他来源获得dCMP氨基水解酶有用。
