Regni Catherine, Schramm Andrew M, Beamer Lesa J
Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
J Biol Chem. 2006 Jun 2;281(22):15564-71. doi: 10.1074/jbc.M600590200. Epub 2006 Apr 4.
The enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) from Pseudomonas aeruginosa catalyzes the reversible conversion of 1-phospho to 6-phospho-sugars. The reaction entails two phosphoryl transfers, with an intervening 180 degrees reorientation of the reaction intermediate (e.g. glucose 1,6-bisphosphate) during catalysis. Reorientation of the intermediate occurs without dissociation from the active site of the enzyme and is, thus, a simple example of processivity, as defined by multiple rounds of catalysis without release of substrate. Structural characterization of two PMM/PGM-intermediate complexes with glucose 1,6-bisphosphate provides new insights into the reaction catalyzed by the enzyme, including the reorientation of the intermediate. Kinetic analyses of site-directed mutants prompted by the structural studies reveal active site residues critical for maintaining association with glucose 1,6-bisphosphate during its unique dynamic reorientation in the active site of PMM/PGM.
来自铜绿假单胞菌的磷酸甘露糖变位酶/磷酸葡萄糖变位酶（PMM/PGM）催化1-磷酸糖到6-磷酸糖的可逆转化。该反应需要两次磷酰基转移，在催化过程中反应中间体（如葡萄糖1,6-二磷酸）会有180度的重新定向。中间体的重新定向在不与酶活性位点解离的情况下发生，因此是持续性的一个简单例子，持续性定义为在不释放底物的情况下进行多轮催化。两种PMM/PGM与葡萄糖1,6-二磷酸的中间体复合物的结构表征为该酶催化的反应提供了新的见解，包括中间体的重新定向。由结构研究引发的定点突变体的动力学分析揭示了在PMM/PGM活性位点中葡萄糖1,6-二磷酸独特的动态重新定向过程中，对维持与葡萄糖1,6-二磷酸结合至关重要的活性位点残基。
