Crystal structure of variant T52P of the intracellular chorismate mutase from Mycobacterium tuberculosis

Unlike typical chorismate mutases, the enzyme from Mycobacterium tuberculosis (MtCM) has only low activity on its own. Remarkably, its catalytic efficiency kcat/Km can be boosted more than 100-fold by complex formation with a partner enzyme. A comparison of wild-type MtCM with naturally and artificially activated MtCMs revealed the overall dynamic profiles of these enzymes as well as key interactions between the C-terminus and the active site loop. In the artificially evolved variant of this model enzyme, this loop is preorganized and stabilized by Pro52 and Asp55, two highly conserved residues in typical, highly active chorismate mutases.

与典型分支酸变位酶（chorismate mutase）不同，结核分枝杆菌来源的分支酸变位酶（MtCM）自身仅具有较低的催化活性。值得注意的是，通过与伴侣酶形成复合物，其催化效率常数kcat/Km可提升100倍以上。通过对比野生型MtCM与天然活化及人工活化的MtCM变体，研究揭示了这类酶的整体动态特性，以及C端与活性位点环之间的关键相互作用。在该模式酶的人工进化变体中，该活性位点环已处于预组织状态，并由脯氨酸52（Pro52）和天冬氨酸55（Asp55）稳定——这两个残基是典型高活性分支酸变位酶中高度保守的氨基酸残基。