Volk S E, Ivanov A G, Baĭkov A A
Biokhimiia. 1995 May;60(5):776-82.
The kinetics of pyrophosphate synthesis catalyzed by rat liver cytosolic and mitochondrial pyrophosphatase in the presence of Mg2+ as cofactor has been studied. According to the kinetic model, this reaction proceeds through two parallel pathways: pathway I utilizing two magnesium phosphate molecules and pathway II utilizing both magnesium phosphate and free phosphate. Pyrophosphate formation is greatly facilitated in the active sites of the enzymes ([E.PPi]/[E.2Pi] = 0.11-0.24). Both enzymes are characterized by high efficiency in pyrophosphate synthesis in solution: the catalytic constants for the cytosolic and mitochondrial pyrophosphatases are 14 and 9.3 s-1, respectively (9 and 16% relative to those for PPi hydrolysis). The results obtained demonstrate that enzyme-catalyzed synthesis of pyrophosphate can proceed at a high rate in the absence of any external energy input, such as that provided by the proton-motive force in membrane systems.
在以Mg2+作为辅因子的情况下，对大鼠肝脏胞质和线粒体焦磷酸酶催化焦磷酸合成的动力学进行了研究。根据动力学模型，该反应通过两条平行途径进行：途径I利用两个磷酸镁分子，途径II利用磷酸镁和游离磷酸。在酶的活性位点中焦磷酸的形成得到极大促进（[E.PPi]/[E.2Pi] = 0.11 - 0.24）。两种酶在溶液中焦磷酸合成方面都具有高效率：胞质和线粒体焦磷酸酶的催化常数分别为14和9.3 s-1（相对于PPi水解的催化常数分别为9%和16%）。所获得的结果表明，在没有任何外部能量输入（如膜系统中质子动力提供的能量）的情况下，酶催化的焦磷酸合成可以高速进行。
