Misset O, Robillard G T
Biochemistry. 1982 Jun 22;21(13):3136-42. doi: 10.1021/bi00256a016.
The mechanism of phosphoryl-group transfer from phosphoenolpyruvate (PEP) to HPr, catalyzed by enzyme I of the Escherichia coli PEP-dependent phosphotransferase system, has been studied in vitro. Steady-state kinetics and isotope exchange measurements revealed that this reaction cannot be described by a classical ping-pong mechanism although phosphoenzyme I acts as an intermediate. The kinetic data indicate that HPr and PHPr occupy binding sites on enzyme I that do not overlap with the binding sites for PEP and pyruvate. As a result, binding interactions between HPr and enzyme I exist regardless of their phosphorylated state. A general mechanism is presented that describes the phosphorylation of HPr. The physiological implications of this mechanism are discussed.
对大肠杆菌磷酸烯醇丙酮酸（PEP）依赖性磷酸转移酶系统的酶I催化的磷酸基团从磷酸烯醇丙酮酸转移至组氨酸蛋白（HPr）的机制进行了体外研究。稳态动力学和同位素交换测量表明，尽管磷酸化酶I作为中间体，但该反应不能用经典的乒乓机制来描述。动力学数据表明，HPr和磷酸化HPr占据酶I上的结合位点，这些位点与PEP和丙酮酸的结合位点不重叠。因此，无论其磷酸化状态如何，HPr与酶I之间都存在结合相互作用。本文提出了一种描述HPr磷酸化的通用机制，并讨论了该机制的生理学意义。
