Srivastava Dhiraj, Razzaghi Mortezaali, Henzl Michael T, Dey Mishtu
Department of Chemistry, University of Iowa , Iowa City, Iowa 52242, United States.
Department of Biochemistry, University of Missouri-Columbia , Columbia, Missouri 65211, United States.
Biochemistry. 2017 Dec 19;56(50):6517-6520. doi: 10.1021/acs.biochem.7b01013. Epub 2017 Dec 1.
Pyruvate kinase muscle isoform 2 (PKM2) catalyzes the terminal step in glycolysis, transferring a phosphoryl group from phosphoenolpyruvate to ADP, to produce pyruvate and ATP. PKM2 activity is allosterically regulated by fructose 1,6-bisphosphate (FBP), an upstream glycolytic intermediate. FBP stabilizes the tetrameric form of the enzyme. In its absence, the PKM2 tetramers dissociate, yielding a dimer-monomer mixture having lower enzymatic activity. The S437Y variant of PKM2 is incapable of binding FBP. Consistent with that defect, we find that S437Y exists in a monomer-dimer equilibrium in solution, with a K of ∼20 μM. Interestingly, however, the protein crystallizes as a tetramer, providing insight into the structural basis for impaired FBP binding of S437Y.
丙酮酸激酶肌肉同工型2（PKM2）催化糖酵解的最后一步，将磷酸烯醇丙酮酸上的磷酸基团转移至ADP，生成丙酮酸和ATP。PKM2的活性受到上游糖酵解中间产物1,6-二磷酸果糖（FBP）的变构调节。FBP可稳定该酶的四聚体形式。在缺乏FBP的情况下，PKM2四聚体解离，产生具有较低酶活性的二聚体-单体混合物。PKM2的S437Y变体无法结合FBP。与该缺陷一致，我们发现S437Y在溶液中以单体-二聚体平衡存在，平衡常数K约为20 μM。然而，有趣的是，该蛋白结晶为四聚体，这为深入了解S437Y的FBP结合受损的结构基础提供了线索。
