Kuettner E Bartholomeus, Keim Antje, Kircher Markus, Rosmus Susann, Sträter Norbert
Center for Biotechnology and Biomedicine, Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany.
J Mol Biol. 2008 Mar 21;377(2):386-94. doi: 10.1016/j.jmb.2007.12.069. Epub 2008 Jan 5.
Arylmalonate decarboxylase (AMDase) from Bordetella bronchiseptica catalyzes the enantioselective decarboxylation of arylmethylmalonates without the need for an organic cofactor or metal ion. The decarboxylation reaction is of interest for the synthesis of fine chemicals. As basis for an analysis of the catalytic mechanism of AMDase and for a rational enzyme design, we determined the X-ray structure of the enzyme up to 1.9 A resolution. Like the distantly related aspartate or glutamate racemases, AMDase has an aspartate transcarbamoylase fold consisting of two alpha/beta domains related by a pseudo dyad. However, the domain orientation of AMDase differs by about 30 degrees from that of the glutamate racemases, and also significant differences in active-site structures are observed. In the crystals, four independent subunits showing different conformations of active-site loops are present. This finding is likely to reflect the active-site mobility necessary for catalytic activity.
支气管败血波氏杆菌的芳基丙二酸脱羧酶（AMDase）可催化芳基甲基丙二酸的对映选择性脱羧反应，无需有机辅因子或金属离子。该脱羧反应对于精细化学品的合成具有重要意义。作为分析AMDase催化机制及合理进行酶设计的基础，我们测定了该酶的X射线结构，分辨率高达1.9埃。与亲缘关系较远的天冬氨酸或谷氨酸消旋酶一样，AMDase具有天冬氨酸转氨甲酰酶折叠结构，由两个通过假二元关系相关的α/β结构域组成。然而，AMDase的结构域取向与谷氨酸消旋酶的结构域取向相差约30度，并且在活性位点结构上也观察到显著差异。在晶体中，存在四个显示活性位点环不同构象的独立亚基。这一发现可能反映了催化活性所需的活性位点流动性。
