Lipscomb W N, Hartsuck J A, Quiocho F A, Reeke G N
Proc Natl Acad Sci U S A. 1969 Sep;64(1):28-35. doi: 10.1073/pnas.64.1.28.
Several features of carboxypeptidase A (CPA) which were previously established by the X-ray diffraction structure studies have now been confirmed by the chemical sequence analysis. These results include the number (307) of amino acid residues in CPA(alpha), the identities of the residues (Arg 145, Glu 270, and Tyr 248) shown by the X-ray study to be involved in substrate binding and catalysis, and the existence of a disulfide bond. The Zn ligands, shown by the X-ray study to be residues 69, 72, and 196 and identified as His, Glx, and either Glx or Lys, are proved by the chemical sequence to be His, Glu, and His, respectively. No change is required in our previous mechanistic deductions, which are here extended to include a specific mechanism of activation of the substrate by a net charge on the metal ion, which suffers a change in local dielectric constant when it is covered by a substrate.
先前通过X射线衍射结构研究确定的羧肽酶A（CPA）的几个特征，现在已通过化学序列分析得到证实。这些结果包括CPA（α）中氨基酸残基的数量（307个）、X射线研究显示参与底物结合和催化的残基（Arg 145、Glu 270和Tyr 248）的身份，以及二硫键的存在。X射线研究表明锌配体为残基69、72和196，分别鉴定为His、Glx和Glx或Lys，化学序列证明它们分别为His、Glu和His。我们之前的机理推导无需改变，在此扩展以包括金属离子上的净电荷对底物的特定激活机制，当金属离子被底物覆盖时，其局部介电常数会发生变化。
