Perret J, Gay P
Eur J Biochem. 1979 Dec;102(1):237-46. doi: 10.1111/j.1432-1033.1979.tb06285.x.
A phosphoryl exchange reaction between fructose 1-phosphate and fructose was found to be catalyzed by a membrane preparation isolated from Bacillus subtilis. The regulation of the biosynthesis of the activity in the wild type as well as in the regulation mutants fruB closely correlates with that of the membrane-bound enzyme II of the phosphoenolpyruvate fructose 1-phosphotransferase system which is known to mediate the transmembrane vectorial phosphorylation of fructose. The computed analysis of the kinetic data shows that the mechanism of the enzyme II is ping-pong, i.e. that a phosphoryl-enzyme intermediate occurs in the reaction. The apparent dissociation constants of the enzyme II/fructose 1-phosphate complex and of the phosphoryl enzyme II/fructose complex are estimated. The value of the standard free energy of the hydrolysis of the bond between the phosphoryl moiety and the enzyme suggests a covalent bonding. This intermediate is assumed to occur in the physiological functioning of the enzyme which utilizes the phosphocarrier protein HPr as phosphoryl donor. The exchange reaction is competitively inhibited by high fructose concentrations: this indicates that the same site of the enzyme binds fructose and fructose 1-phosphate, this site being accessible to fructose on the external side of the membrane when the enzyme is phosphorylated.
从枯草芽孢杆菌中分离得到的膜制剂可催化磷酸果糖-1与果糖之间的磷酰基交换反应。野生型以及调节突变体fruB中该活性生物合成的调节与磷酸烯醇丙酮酸-果糖-1-磷酸转移酶系统的膜结合酶II密切相关，已知该酶介导果糖的跨膜向量磷酸化。动力学数据的计算分析表明，酶II的机制为乒乓机制，即反应中会出现磷酰化酶中间体。估算了酶II/磷酸果糖-1复合物和磷酰化酶II/果糖复合物的表观解离常数。磷酰基部分与酶之间键水解的标准自由能值表明存在共价键。假定该中间体存在于利用磷酸载体蛋白HPr作为磷酰基供体的酶的生理功能中。高果糖浓度可竞争性抑制交换反应：这表明酶的同一位点结合果糖和磷酸果糖-1，当酶被磷酸化时，该位点在膜外侧可被果糖识别。
