Pakhomova Svetlana, Luka Zigmund, Grohmann Steffi, Wagner Conrad, Newcomer Marcia E
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA.
Proteins. 2004 Nov 1;57(2):331-7. doi: 10.1002/prot.20209.
Glycine N-methyltransferases (GNMTs) from three mammalian sources were compared with respect to their crystal structures and kinetic parameters. The crystal structure for the rat enzyme was published previously. Human and mouse GNMT were expressed in Escherichia coli in order to determine their crystal structures. Mouse GNMT was crystallized in two crystal forms, a monoclinic form and a tetragonal form. Comparison of the three structures reveals subtle differences, which may relate to the different kinetic properties of the enzymes. The flexible character of several loops surrounding the active site, along with an analysis of the active site boundaries, indicates that the observed conformations of human and mouse GNMTs are more open than that of the rat enzyme. There is an increase in kcat when going from rat to mouse to human, suggesting a correlation with the increased flexibility of some structural elements of the respective enzymes.
对来自三种哺乳动物的甘氨酸N-甲基转移酶（GNMTs）的晶体结构和动力学参数进行了比较。大鼠酶的晶体结构先前已发表。为了确定人源和小鼠源GNMT的晶体结构，它们在大肠杆菌中进行了表达。小鼠GNMT以两种晶体形式结晶，一种单斜晶型和一种四方晶型。三种结构的比较揭示了细微的差异，这可能与酶的不同动力学性质有关。活性位点周围几个环的柔性特征，以及对活性位点边界的分析表明，人源和小鼠源GNMTs观察到的构象比大鼠酶的构象更开放。从大鼠到小鼠再到人，催化常数（kcat）增加，这表明与各自酶的某些结构元件的柔性增加相关。
