Jedrzejas M J, Chander M, Setlow P, Krishnasamy G
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
J Biol Chem. 2000 Jul 28;275(30):23146-53. doi: 10.1074/jbc.M002544200.
The structure of the complex between the 2, 3-diphosphoglycerate-independent phosphoglycerate mutase (iPGM) from Bacillus stearothermophilus and its 3-phosphoglycerate substrate has recently been solved, and analysis of this structure allowed formulation of a mechanism for iPGM catalysis. In order to obtain further evidence for this mechanism, we have solved the structure of this iPGM complexed with 2-phosphoglycerate and two Mn(2+) ions at 1. 7-A resolution. The structure consists of two different domains connected by two loops and interacting through a network of hydrogen bonds. This structure is consistent with the proposed mechanism for iPGM catalysis, with the two main steps in catalysis being a phosphatase reaction removing the phosphate from 2- or 3-phosphoglycerate, generating an enzyme-bound phosphoserine intermediate, followed by a phosphotransferase reaction as the phosphate is transferred from the enzyme back to the glycerate moiety. The structure also allowed the assignment of the function of the two domains of the enzyme, one of which participates in the phosphatase reaction and formation of the phosphoserine enzyme intermediate, with the other involved in the phosphotransferase reaction regenerating phosphoglycerate. Significant structural similarity has also been found between the active site of the iPGM domain catalyzing the phosphatase reaction and Escherichia coli alkaline phosphatase.
嗜热脂肪芽孢杆菌的2,3-二磷酸甘油酸非依赖性磷酸甘油酸变位酶（iPGM）与其3-磷酸甘油酸底物形成的复合物的结构最近已得到解析，对该结构的分析有助于阐明iPGM催化的机制。为了获得该机制的更多证据，我们解析了该iPGM与2-磷酸甘油酸和两个Mn(2+)离子形成的复合物的结构，分辨率为1.7 Å。该结构由两个不同的结构域组成，通过两个环连接，并通过氢键网络相互作用。该结构与提出的iPGM催化机制一致，催化过程的两个主要步骤是磷酸酶反应，从2-或3-磷酸甘油酸中去除磷酸，生成酶结合的磷酸丝氨酸中间体，随后是磷酸转移酶反应，磷酸从酶转移回甘油酸部分。该结构还确定了酶的两个结构域的功能，其中一个参与磷酸酶反应和磷酸丝氨酸酶中间体的形成，另一个参与再生磷酸甘油酸的磷酸转移酶反应。在催化磷酸酶反应的iPGM结构域的活性位点与大肠杆菌碱性磷酸酶之间也发现了显著的结构相似性。
